This is just an observation, but I've noticed lately (within the last week, probably) that some people's avatars are missing. The pictures are replaced with a broken image icon. As an example, in a recent post (http://www.homebrewersassociation.org/forum/index.php?topic=15826.0), the avatars for poobah85, mabrunguard, and davidgzach are missing, while they are there for hopfenundmalz, HoosierBrew, and brewmasternpb.
Not sure what's going on. I just went to that thread and every avatar shows up fine.