I've been thinking about something related the last few weeks, which I guess I may as well suggest.
I think that most of the potential uses of the subscribe feature are lost. For example, I might want to subscribe to Boxslayer's thread in the CFB forum to be alerted when he posts selections, but it's useless because I just get spammed with random comments that are of no interest. Similarly I might want to be alerted when Homedawg or Railbird post in the CBB forum, but I can't because they use a different thread each day (and even if they didn't, the first problem would still arise).
There must be (or it would be easy to write, given it's just an SQL query) a VBulletin plugin to subscribe/e-mail when (thread=729463 & poster=Boxslayer(, or (forum=111 & poster=Homedawg). That would be far more useful than the current offering.