The patent is valid as of the issue date. A re-examination request can be filed at any time during the life of the patent.
I haven't yet heard what, if any, formal relationship AskPatents.com will have to the examination process going forward. However, at least for an already-issued patent a re-exam would be required.
I wonder if it would be possible to collect some prior art, then call up a patent holder and shake him down for a little "settlement" to keep you from filing the re-exam.
From my understanding the director of the patent office David Kappos, was the one that asked the people at stack exchange to make this site. I suppose they indeed haven't given any further details of how they will interact, but I don't see him taking this initiative without intending to bring to the attention of his office the patent questions which receive the highest votes. (seeing that is how stack exchange works anyways.)
The promotion by the director is a great sign, and I can see AskPatents being very useful for prior-art searches (one of the results of which is the NPL document referenced above). It will hopefully improve results and save money.
Absent some statutory changes, it's hard to see how it will impact the prescribed, formal steps of the patent review process. Patent filings are a lot more complicated [edit: as compared to existing legal forms websites], but I can imagine a template interface that would allow crowd-sourcing before a final review to cross the Ts and dot the Is.
It would be phenomenal if the PTO streamlined the process themselves. Baby steps...
I haven't yet heard what, if any, formal relationship AskPatents.com will have to the examination process going forward. However, at least for an already-issued patent a re-exam would be required.