In both Ubuntu 10.04 and 12.04, a perfectly happy sleeping laptop is woken when moved. Either the HD-shock detection, the trackpad or a sloppy key will wake it when the lid is closed.
To test this I suspended the computer and left it for 5-10 minutes where it slept nicely with the lid open. Then pressing the Fn-key would wake it in 12.04. In sleep mode with the lid closed, moving the laptop wakes it. Sometimes it immediately goes back to sleep, but not always. It's a laptop and I put it in a bag to carry to and from work, so being asleep is kind of important.
I'm hoping someone can suggest a way to debug.