One of the nifty things your PSVita can do is remote play you PS3 games over a wireless network. That is, if the feature is enabled for the game you want to play. As it stands, I'm not aware of any PS3 games that actually work with this feature, but I was able to play the digital download version of Final Fantasy IX for PSone on my Vita via remote play.
Here's the kick, we've been somewhat led to believe that some kind of programming in the PS3 game would be required in order for this to work. It turns out though it's simple a matter of a tick box to turn the feature on or off. In fact, every PS3 game is currently capable of being played remotely, without any update to the actual game. The feature itself is actually controlled by the PS3 firmware. Being that this is the case, custom firmware for the PS3 has popped up which allows for remote play of all PS3 titles on the Vita. A video demo of someone playing Battlefield 3 on their Vita via remote play below shows that it is indeed possible.
So why is it that all games have remote play disabled by default? Why money of course. If you can play your PS3 titles on your Vita, then you're less likely to buy the Vita version of that game, should one be released. This is the only logical reason for disabling support for remote play, and it's sad that the feature ends up being dead on arrival because of it.
Let me ask you this; when was the last time you bought both a console and a portable version of the same game? Sony should be embracing this feature as a way to take the wind out of the Wii U, instead of crippling it.