Why do you need so many accounts for? Link building to your money site?
A few years ago (maybe roughly 2005-2008) you could easily get to the top of the serps by putting doorway pages on high PR free hosts and spamming them. Google was just starting to put the dampeners on brand new domains, but using trusted hosts was an easy way around that. No mucking around with linking to money sites or "link wheels" as people like to call them now - you could just put up a generated keyword stuffed doorway page and use javascript redirects to drive the traffic wherever you wanted.
They'd get deleted by the free hosts soon enough, but as long as you could create more than they banned automatically you would be ahead of the curve. At one point I was putting up several hundred sites a day.
For example, some readers might be familiar with the free host 0catch.com. 0catch had a backend that allowed people to set up their own domains as free hosts, all with the same sign up script. I identified 80-100 domains with good PR (4+) that all used the 0catch backend and thus all had the same signup script. My bot would sign up for an account at each of these 0catch domains every day, generate and upload a site, then add the urls to the list of stuff to get link spammed. So that would be 80-100 new accounts and sites each and every day, just from that 0catch stuff... Plus there were umpteen other free hosts I was plundering. And I was small fry in the grand scheme of things eg. compared to some of the heavy duty viagra spammers.
Unfortunately, 0catch and most other free hosts are spammed to hell now because of people like me and most of those old free host domains are penalized on the domain level. Most (but not all) web 2.0s and free hosts disable javascript now, so using doorway redirects on them isn't so possible any more. People have started using free hosted sites as buffers to their money sites instead of using them to drive traffic directly.
But the principle still holds true for the web 2.0 link wheel sites and "trusted" free blog hosts of today - automation and robust anonymity rule. Never do something by hand that you can get a script to do. You just gotta fly under the radar and stay ahead of the banning curve.
Anyway long story short - signing up for free accounts is something I know a bit about.
