I'll save you some time with this protip: More than half of the registered users were created by bots & are lying dormant, waiting ... for your Bitcoinz 
Yep, they're a commodity, to be bought and sold.
Yep, they're a commodity, to be bought and sold.Why these have value when you can create new yourselves
The short answer is: captcha. Anyone can write a script to automate registration, but solving a captha? Even virgin accounts, with no posts, are valuable in bulk. If the registration date is reasonably old? +1 clout.
In these toobz, people judge each other on weird metrics -- acount age, # of posts. BTW, there's an open thread soliciting accounts, so if your post count is high enough, your account is worth money to someone