I think I have at least 3, the first one is when I first joined...and just browsed every now and then, stopped coming for a couple of years, moved and couldn't even remember my username, so another account, then I moved again changed internet providers, when I came back here...forgot username and couln't even find my old renders, that happened twice, this new one my husband started and now I've taken it over and I attached it to my yahoo account so I don't have to worry about what provider I'm with.  
But I know people on the site who at one time had three different usernames just so they could post more stuff.  Just thought of a new thread: Renderosity seems to be the biggest money making Poser site around (seems, Daz3D is doing quite well too, but they have their own products) but when i go to other sites, I can post 3 images a day and here only 1...kinda...weird dontcha think, RDNA...3, Renderotica...3....Renderosity ....1 or if you pay (LOL) 3

Oh almost forgot I knew someone here that had a seperate account just so he could comment on his renders, this was a couple of years back and then I started commenting on them because no one else would, as a reward if you can call it that he would always comment on my images with both usernames and click the "vote" (remember that option?) with both of them. He's still on the site but no longer has the same comment issues...it's funny because at one time he would get 3 comments (two from himself and one from me) and I would have a modest 10 or 15...now he puts up anything and gets at least 30 plus and I struggle for four and at least one of those comments comes from someone I know in real life.  My husband is starting a new account so I'll have at least one more steady commenter!! LOL