I used to do that in the past, not now anymore.
Sometimes, there were only ONE (or nearly one) forum for a specific topic of interest, so most of us signed up for that forum. Later, along the way, when we find out there's another newer forum for the same TOI; some of us would join the newer one, sign up with the same signature, photos, posts etc. Wouldn't that be kind of duplicating oneself in multiple places?
Let's hear about why some of us actually join multiple forums - especially posting the same shots, when the TOI is the same.
For myself, I believe I have a now-dormant Offstone account somewhere, and totally out of use now, just because at a point of time, some friends told me the other forum had somewhat more "artistic" inclinations.