As everyone knows, if a user registers in bbpress instead of through wordpress(mu) that user doesn't get a default role set.
I've dug and dug on both the bbpress and wpmu forums and haven't found a fix for this. I did find a fix that apparently works for wordpress, but I tried it for wordpress mu with no luck.
The 4th post in this thread explains a way to set roles in wordpress mu.
I imagine that a plugin with the combination of the two solutions would allow users to register through bbpress and get a default role on the main wordpress mu blog. But, unfortunately I have no clue what I'm doing. If anyone has a free minute or two to look at the bits of code and maybe hack something together that would be awesome.
Oh, and I'm using the latest versions of both bbpress and wpmu.