I Am Sam Altman, President of Y Combinator. AMA

Unlike most other programs, YC does not have mentors--just partners that spend all their time advising startups (and some part-time partners).

This is really important--most people give terrible startup advice, and people that do nothing but select and advise startups all day are probably the best source of good startup advice.

We split into 4 groups, and each company gets 2-3 "group partners" as their main points of contact. We encourage you to talk to these partners at least once a week, and then other partners whenever you need their specific expertise.

Slow growth is bad, yes. A lot of our questions will be about why it's slow and how you plan to make it faster.

We tell startups during YC to shoot for 10% weekly growth in their key metric.

It is often on the first time. The 7th time is the highest count I know of. It's common for it to be on the second or third time.

If we reject a company at interviews, we'll say what our objection is. If you reapply and that isn't fixed, you're unlikely to get in.

More generally, fast progress is something we really look for when deciding to fund startups.

Personally, I think it's super interesting. LendUp is a company we funded a few years ago, and we've done more recently.

We never set this ahead of time--it really depends on how many companies apply that we want to fund, subject to the constraints of how hard the parters can work.

I'd guess in the range of 100-130, based on current application volume. We had a big spike in growth last batch (I think because of the startup class).

The apparent cause is running out of money, but the real cause is failing to build something users love. It is usually apparent in the first 6 months, but not always.

Another big cause is cofounder tension.

I might do a sort of graduate school version--i.e. "How to scale a startup"

It's hard to give a standard answer to this--it depends entirely on the specifics of each case.

The evolution of the university. But I think it's a much better model--it's got just the right amount of decentralization, it attracts the best people in the world to one place because of the network effect, we pay you instead of the other way around, instead of asking for donations of our alumni in the future we'll let them invest in the ecosystem, etc. And I think you learn far more in 3 months of YC than 3 months of university.

YC is fundamentally just a hub of smart people that help each other.

I think there is some chance that the total aggregate market cap of YC companies by then is approaching the largest market cap of any company (though a safer bet would be 20 years from now). I hope that we'll have funded many of the most important companies, and been able to help them quite a bit. I'm pretty sure the network will be powerful.

I'm sure we'll also do new things that seem crazy today, e.g. a fundamental research lab.

We are excited about teams applying for anywhere in the world! A huge percentage of the startups we fund come from outside the US.

Not much it seems. :)

I have a slack channel I'm growing that's open to all aspiring developers and entrepreneurs to eventually solve this exact problem. Check this page for more info, http://www.openmindedinnovations.com/about. Just email me at jbhatab@gmail.com if you're interested :).

This is 2015 - clearly it's not possible to found a company without living in a tech hub ;)

Unclear communication. It's surprising how often we get 5 minutes into an interview without being able to really understand what a startup does.

Counting companies that have raised with SAFEs but not equity rounds, probably about 250-300.

Great question! The biggest mistake founders make is burying whatever it is that's exceptional about them or their company deep in the application.

We are optimists. We want to believe. Help us by putting whatever it is that is going to make us want to fund you early in the answer to each question.

Also, be concise.

I imagine each partner will have different answers. One thing I say is that we should be willing to fund anything that could be a $10B company, and that is such a difficult restriction we shouldn't have any other restriction.

Personally, I am very interested in nuclear energy and solar (I think energy is the highest-impact single thing to fix--it's remarkable how many other problems reduce to the energy problem), biotech, AI, education, healthcare, and online communities.

Interestingly, those first three categories are also where I think the biggest dangers to humanity are. High-risk high-reward, I guess.

The most common thing is getting founders to focus on the right thing. At this stage, nothing but building a product that users love matters. Founders want to focus on anything else, and have wonderfully detailed excuses for why whatever it is is so important.

"Write code and talk to users" is not sexy, but it's the road to success. Seeing your name in the press is sexy, but unfortunately has nothing to do whatsoever with actual success.

There is no shortcut for the hard work of building a great product.