The ones that do it now seem to do it with sign-up friend invites. The best thing to do is fire up one of the adders that can bypass the captchas, and use ethereal to see what type of form variables are being sent back and forth.
If I remember correctly, Pwntcha is not a program. Pwntcha is just a series of image manipulations designed specifically for a given captcha. You still have to figure out how to defeat the captcha on your own. But, with the pwntcha toolkit, you can automate the sequence once you have it. If you are interested, here's some interesting links:
You just need to refer a friend and then you are good for 430 or so friends after that, that is what the bots do in the background, it is not rocket science guys
