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Mark Castillo @markcastillo

👋 webdev, occasionally RT San Francisco Bay Area Joined February 2007
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Mark Castillo retweeted
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Y Combinator @ycombinator

4 weeks ago

Introducing the YC Early Access Network. 4x a year, senior technology leaders get early looks at YC's enterprise AI companies and help shape their roadmaps. Invite-only, by application. Fall '26 kicks off Oct 22 in SF. Apply now: events.ycombinator.com/yc-early-acces


Mark Castillo retweeted
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Y Combinator @ycombinator

2 months ago

In 2005, @sama was a Stanford sophomore in YC’s first batch, building a startup in a little Cambridge office while @paulg cooked the founders dinner. Twenty years later, as co-founder & CEO of OpenAI, Sam closed Startup School 2026 in conversation with @garrytan — on agents, ambition, and why the ceiling for what a startup can take on has never been higher. 00:07 — From YC’s First Batch to Today 03:04 — What PG Taught Sam 04:17 — Why Startups Matter More Than Ever 06:57 — The Coming Golden Age of Ambitious Startups 09:30 — Why Startups Win During Technology Shifts 11:46 — Building OpenAI When Nobody Believed in AGI 14:45 — Finding People Who Share Your Conviction 18:05 — Help People Before You Know Why 19:43 — Earnestness, Ambition, and Ignoring the Haters 24:04 — The AI Safety Incident That Changed the Stakes 26:58 — Preventing AI From Concentrating Power 30:41 — How Fast AI Models Will Improve 36:06 — The Best Version of an AI Future 37:47 — “It’s All Going to Work Out”

Mark Castillo retweeted
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Y Combinator @ycombinator

11 months ago

"If you want to do great work it's an advantage to be optimistic, even though that means you'll risk looking like a fool sometimes." Paul Graham on earnestness and doing great work:

Mark Castillo retweeted
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Aakash Gupta @aakashgupta

3 years ago

The pace of AI remains insane đŸ€Ż All these announcements in the last 7 days: Zapier AI Bard Images Mind to Video Google AI Ads Photoshop Fill Bing x ChatGPT Windows Copilot Perplexity Copilot DragGAN Image AI Google SoundStorm Here's everything you need to know:

Mark Castillo retweeted
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Yin Wu @yinyinwu

4 years ago

There's a lot of advice on how to scale a startup... But there's little on how to shut down a company when things aren't working. Here are the tactics for dissolving a startup, and what to tell investors to get them to fund your next bet 👇

Mark Castillo retweeted
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Garry Tan @garrytan

4 years ago

2022 YC Year in Review There are now 316 alumni valued at over $150M 80 are valued at over $1B Total value of YC companies is over $600B Many thanks for an amazing year ⁊@gralston⁩ 🙏 ycombinator.com/blog/2022-yc-y


Mark Castillo retweeted
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Michael Seibel @mwseibel

4 years ago

I’ve found that YC founders, consciously or subconsciously, choose to meet with a particular YC partner to consume a very specific experience (like choosing a restaurant).

Mark Castillo retweeted
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Michael Seibel @mwseibel

4 years ago

It's surprising how often startups will copy their competitor's features rather than talk to their users. The best startups understand they cannot outsource one of the most important parts of building a successful product.

Mark Castillo retweeted
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10-K Diver @10kdiver

5 years ago

1/ Get a cup of coffee. In this thread, I'll walk you through the art and science of valuing a company. The Goal: We want to figure out how much a company is worth -- so we know what's a good price to pay for its shares.

Mark Castillo retweeted
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Y Combinator @ycombinator

5 years ago

Moni uses a community-driven model based on social trust to provide financing to mobile money agents across Africa, achieving 99% repayment with 10,000+ loans disbursed so far. Welcome to YC, @femi_iromini, @Adesobayo, and team @moni_africa! ycombinator.com/companies/moni

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Rank App @rankapp__

5 years ago

We’re excited to announce that we’re part of the @ycombinator W22 batch. @moni_africa uses a community-driven model based on social trust to provide financing to mobile money agents across Africa in 5 minutes. Learn more about what Moni is building at moni.africa

Mark Castillo retweeted
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Y Combinator @ycombinator

5 years ago

We're excited to announce our new standard deal at Y Combinator. When a company is accepted into YC, we now invest a total of $500,000. @gralston shares more on our blog: blog.ycombinator.com/ycs-standard-d


Mark Castillo retweeted
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Y Combinator @ycombinator

5 years ago

We're hiring for a programs & ops person with a recruiting background to help scale YC's workatastartup.com platform, where we helped ~600 people find jobs in 2021 alone. If you or someone you know might be a fit, check out the role and apply here: ycombinator.social-previews.top/dpssmn

Mark Castillo retweeted
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Shriya Nevatia @shriyanevatia

5 years ago

OK so who wants to break into VC in 2022? 👀💰🚀

Mark Castillo retweeted
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10-K Diver @10kdiver

5 years ago

1/ Get a cup of coffee. In this thread, I'll walk you through a somewhat counter-intuitive relationship: When a company is aggressively buying back shares, long-term owners can actually *benefit* if the company's stock price stays low for a while.

Mark Castillo retweeted
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Kolby Hatch @HatchKolby

5 years ago

Chrome is used by 2.65 BILLION people. That's ~56% of all internet users. You're probably one of them. 95% of my job is done inside Chrome. So a few years back, I learned 6 hotkeys to use Chrome FASTER. Here they are 👇

Mark Castillo retweeted
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GV @GVteam

5 years ago

“Optimism, creativity, and grit are three essential tools in my design process. I approach every problem knowing there is a solution,” says GV Lead Operations Partner @katearonowitz in @FastCompany — fastcompany.com/90667673/want-


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Mark Castillo @markcastillo

5 years ago

@garyvee 👋

Mark Castillo retweeted
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seedphrase @seedphrase

5 years ago

Nobody cares about how many dollars are in your bank account, how many Lambos you own, or your rare baseball card. We only care about jpegs. This is the only flex metric that matters.

Mark Castillo retweeted
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Gary Vaynerchuk @garyvee

5 years ago

big day

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Chad B @LockdownCB

5 years ago

I just spent $500 on books to get 1 NFT 😂 Shoutout Gary for getting me to read more

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Mark Castillo @markcastillo

5 years ago

@DeadAssNFTs @bobbyhundreds đŸ”„đŸ”„đŸ”„

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