(http://i.imgur.com/REk2h.png)
It seems some readers tipped off 'AndroidPolice' on a neat trick you can do with your Nexus 7 Tablet to get more than just one $25 credit towards Google Play content. It requires a bit (although not too much) of hassle but if you factory reset your device and log in to a new account during startup you get a new $25 credit. Each time.
Now keep in mind you'll have to have a credit card attached to each account so theoretically as many different cards that you have you could do this with each. Now we're not condoning this kind of thing. We doubt it's Google's intent...although it wouldn't be crazy to think that more than one person could use a tablet and therefore each person could be given their own $25 in free credit to try out apps. As far as we know there's no $25 per tablet rule that's been stated. We wouldn't be surprised if Google issues a fix that prevents this sooner than later.
source: AndroidPolice (http://www.androidpolice.com/2012/07/18/christmas-in-july-logging-into-the-nexus-7-from-multiple-accounts-gives-25-credit-in-each/)