I started tabbing songs three or four years ago - in a fit of nostalgia, I decided to play a song we covered every gig back in the previous century, and I couldn't remember it! I had to figure it out again and decided I'd better write it down this go around.
Not long after, I discovered the BassMasta web site. Eventually, I uploaded my tabs there, only to delete them all when the owner sold the site to Songster.
As BassMasta died, there were a number of efforts to start up new sites and keep the community of BassMasta users together: two of these which I tried to help make work were Bass Haven (a bass forum) and Bass Place (a tab site). I have put some of my tabs from BassMasta on both of these sites, but technical issues arose making posting a problem (could log in, then couldn't, required formats other than what I normally use…

Presently, Big Bass Tabs is the only tab site I post tabs to, as it is the most BassMasta-like that I have found. I hope that this site eventually becomes what BassMasta was (a helpful community where you could ask a newbie question and not get shit for it, with lots of tabs - some of them quite good), and am trying to help that happen.
That said, I think posting your tabs on multiple sites is a good thing for persons trying to learn a song or how to play. Tab sites appear, get the letter from the recording industry's lawyers, and disappear - or sell out. Redundant postings help keep the info available and on the net.
Cheers.