Your "people you know" are liars.
I created a new Battle.net account, but I'm unable to opt in. Why?
In order for a Battle.net account to be able to opt in to upcoming beta tests, you must have at least one Blizzard Entertainment game attached to the account. Please note that the World of Warcraft trial edition does not count toward this requirement.
found here:
http://eu.blizzard.com/support/artic...ategoryId=4301
Yes, you have to have an active account, if not, you can't be selected for the beta. That's how it was for TBC and WotLK, there's no reason to assume it would change.