Quick heads up since a number of folks have noted/asked about this: yes, the search function for logged-out readers is currently not working. It throws up a complaint that is unhelpful but also not dangerous: "Unauthorized access to internal API. Please refer to...". We'll have it fixed soon, but just a heads up that (a) it is indeed a thing and (b) it's not something to worry about. Sorry about the annoyance!
This article from June 12 has a lot of useful up-to-date info and context about how MetaFilter was penalized. There is also some discussion about a potential solution (although Matt Cutts is being typically cryptic) in coming "weeks or months."
I was initially trying to read the metafilter post There's No Avoiding Google+ and I kept getting a server error: Your Browser: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31 [more inside]
Did I hallucinate a Metafilter comment? I remember reading the line "Play him hither, Lute Cat" on Metafilter recently and though it was so hilarious I needed to illustrate it. I wanted to give credit to the original commenter, but I can't for the life of me find the comment. All my styles of google-fu have failed me. Did this comment actually exist?