Actually, I find the other social networking sites are a little less distracting, as you have a little more control on the information flow. For Twitter, I use Twitterfox... and sometimes I simply don't log on
It's important for me to keep up with social networking sites and tools, since this is one of the main areas I help other small businesses with. The more we go ahead, the more it seems to become a never-ending list. My rule is to pick the ones that work best for me and play around with the others, in my leftover time, when I'm just doing that... playing around! You never know where a good idea can come from!
Just curious to hear about other fellows VAs tweeting habits: I see busy professionals tweeting the whole day, say once every 10 min., I suppose they have a "ghost-tweeter"!

thanks for your answers!
Alessandra
(from Italy!)