The issue isn't necessarily collecting "boatloads of data"; rather, the problem is making sure I have a way to contact this person who is potentially interested

The issue isn't necessarily collecting "boatloads of data"; rather, the problem is making sure I have a way to contact this person who is potentially interested in my product. For you, this is conveniently solved through their screen name and network. However, how would you go about contacting someone who stumbles upon your website (without explicitly asking them for contact info)? Another issue is accountability. If someone is abusing my service, I want to be able to ban them from ruining things for everyone else. If you look at sign up forms in terms of security, the psychological acceptability of filling out a form and providing an e-mail address is actually quite high compared to more robust ways of verifying identity (driver's license, social security number, etc).