Perhaps my favorite thing about Ask Metafilter is when someone asks a question that could best be answered by a very particular, obscure kind of expert, and then that exact expert shows up and answers, expertly. Can you post great examples of that here? The more perfectly precise the match between the needed expert and the one who shows up, and the more improbable it is that the right expert would have come along and answered, the better. [more inside]
What are some MeFi usernames which match their users' expertise? For example, physicsmatt comes in to set things straight regarding physics posts. And backseatpilot can be relied upon to supply intelligent aviation-related info. Who else comments pretty much exclusively on topics represented by their username?
What if you really could page users -- alert them to a thread they would interested and/or helpful in?