The big difference is that beta gmail could communicate with email from other providers. So it was exclusive but not really closed - you had a rare domain name,

The big difference is that beta gmail could communicate with email from other providers. So it was exclusive but not really closed - you had a rare domain name, a huge inbox and the ability to send other people invites - that was pretty cool for 2005. That's nothing like the Google+ launch - making that a closed beta was death from the start because you could only interact with the few other people in the closed beta.