One thing that isn't often mention is this: the average time to liquidity for a venture backed startup is just north of 7 years [edit: make that 8.7 years].
The first "class" was 6/2005:
Reddit (made it pretty big)
Infogami (joined reddit, "made it big")
Kiko (sold for ~$250k, started Justin.tv - likely to make it big)
Loopt (well-funded, great traction, seems likely to make it pretty big)
ClickFacts
Firecrawl (one founder joined TextPayMe, another YC company that sold to Amazon)
Simmery (one founder joined Reddit and presumably made it sorta big)
Memamp
--> That's 50-75% seeming to have a pretty good shot at making it somewhat big.
I would expect the exact opposite. In 2005 many were skeptical of the whole YC model, and consequently would have had a much more difficult time attracting investors and already-successful startups. The first demo day was twelve investors, mostly PG's friends; the S10 demo day was a three-day affair with over 350 investors and members of the press. The current batch also was able to attract some startups which already had launched and had good traction before YC even started; these startups probably would not have applied to the first couple YC batches because it was not yet clear just how advantageous YC was even for startups which could raise at higher valuations.
YC's star is rising still-- the most recent "class" was pretty epic IMO. It's not a talent show-- it's a hacker-optimized machine that's always getting better at picking, mentoring, promoting, and funding teams/startups.
"Lisa Lambert, Vice President at Intel Capital, said:
It just takes a long time to go from startup idea to a liquidity event. [...] During the boom days, it was like 2.6 years to get liquidity. And today, the latest average from NVCA, the National Venture Capital Association is 8.7 years."
The first "class" was 6/2005: Reddit (made it pretty big) Infogami (joined reddit, "made it big") Kiko (sold for ~$250k, started Justin.tv - likely to make it big) Loopt (well-funded, great traction, seems likely to make it pretty big) ClickFacts Firecrawl (one founder joined TextPayMe, another YC company that sold to Amazon) Simmery (one founder joined Reddit and presumably made it sorta big) Memamp
--> That's 50-75% seeming to have a pretty good shot at making it somewhat big.
You can head to: http://spreadsheets.google.com/ccc?key=0AkkhSN3vaY4jdF90b1l1...
and do your own math, but it's pretty premature for most of the classes.