The jury's still out on Google's new mobile approach to email, but that hasn't stopped people from going a little batty over getting invited to use it (see also: Gmail, Google Wave). In case you were feeling a little weird about begging Google for an Inbox invite, though, you can now just beg your Inbox-using friends for one. Google has just started gracing users with three invites to spread among their needy peers -- if they happen to see a golden ticket (we really need a new visual metaphor to that effect) in their Speed Dial menu, they can start spreading the love. Alas, Google isn't letting the floodgates fully open just yet: if you got your invite from someone who didn't get theirs straight from Mountain View, chances are you don't have any invites of your own to share. Now we're just waiting to see if a secondary market of Inbox invites springs up -- what's the Bitcoin-to-Inbox invite ratio these days?