1script - 2:17 am on Aug 24, 2012 (gmt 0)
They can and they already do. I've been collecting data about this for most of August and even though one month is probably not very significant statistically, what I see is that my Google traffic to questions with no responses is a meager 1.21% of my overall G traffic which makes them 10 times less likely to receive a visit from Google SERP (about 12% of the questions don't have answers on my site). So, if feels like no matter whether I do no-index or not, it will only affect a tiny fraction of the traffic. It's actually hard to believe that anything having to do with such small part of a site can affect the site as a whole but Google seems to work in mysterious ways...
In fairness though, it's not like Google couldn't just ignore those results.
On the other hand, if it comes with at least some hope for escaping a next Panda refresh, 1% of the traffic is certainly worth it.