Not really.

Roger Ehrenberg has been writing some great posts on what went wrong with his company (Monitor110) at informationarbitrage.com, and has been getting some great feedback.

They can leave the private stuff to themselves, but it wouldn't be completely unreasonable for a y-combinator-funded company to at least briefly post a "what went wrong" for the benefit of future startups. They'll still have all their knowledge and experience, and sharing that won't take it away from them.

Doesn't mean it must happen public. You can be certain when someone decides to shut down they've already had that kind of discussion, with people the would like to share these thoughts.

if their plan was flawed, then sure, they could let others waste time to come to the same conclusion, but that seems mean to me. If they'd rather not say though completely up to them.

I think it is interesting though, as web OS things were hyped up at one point. It'd be useful to know if youos shutdown because the plan was flawed, or for some other reasons.