Unfortunately even the invites that people were saving are now locked on the site. Per their forums, this is not a glitch but a change to the site for the foreseeable future. So even if someone has the desire to give an invite, there are simply none left to give, which is a bummer.
I don’t know what the root cause was for that decision, but I can imagine it has a lot to do with newcomers having crappy ratios. Not one of the people I provided an invite to has a ratio over 1. I know that a few of them are trying to seed, but it still paints a somewhat ugly picture.