Re: bbpress and memcache?
Output caching can be effective for parts of the page (I do it in several plugins) but caching an entire page for a forum is not as good of an experience for forums vs blogs.
Blogs are post once, read many times. Forums are post many times, read many times.
When you aren’t viewing comments, blogs barely change, on forums everything changes constantly.
Unless you don’t mind showing guests outdated info.
One day someone will port WP Super Cache or similar (but don’t look at me).
It will be effecting for showing guests outdated info.