It's not a fake life online, but one that doesn't reveal personal information. At least that's my case. In joining discussion forums, I don't use my real name (obviously the case here...it's the title of a Nick Drake album) or my real picture (I'm not really Aaron Rodgers in a throwback Packers uniform). People understand that, generally, no one uses their real names or photos on a message board. While registration is required, this is still a pretty public place since registration isn't really restricted--other sites might be invitation-only, for example, or require administrator approval before an account is active. I don't take withholding personal information to be deceptive but rather, understandably, keeping your guard up because we are all pretty much strangers until people get to know each other better.
Using real names and photos via IM or e-mail comes later and there, at least, it seems that if your sole motive is to make friends then there really isn't much to be gained by lying. That's how I behave, anyway.