[uptown]

It's easier to get friends to sign-up for a service when they receive an email saying you've shared something with them, and linking to the app-download page.

That's what was alleged to have happened with blasting invites to people's entire contact list against their will.

http://www.branded3.com/blogs/the-antisocial-network-path-te...

With that said, from a mathematical standpoint it's difficult to see how this could be a widespread thing. If everybody that joins Path had this happen, it'd eventually become a massive problem where everybody with a phone would be receiving these texts (think six degrees of Kevin Bacon) - so I suppose it's possible this isn't happening to all users.