How fast does a processor have to be to mine bitcoins I have a MacBook Air running 10.7(Lion) with an Intel Core i5 processor

I want to try to mine bitcoins for fun. I understand that I alone will probably not be able to get any bitcoins from mining so I registered for some mining pools (Slush's pool, BTC Guild) and tried various applications to try to mine (MacMiner, guiminer, and cgminer)

For all of these, I am able to connect to the mining url with my credentials. guiminer shows that I have a speed of about 2 MH/s. However, nothing else seems to happen even after running these programs for about half an hour. I don't seem to be contributing to any of these pools.

Can someone tell me what is going on wrong?
After the creation of specialized hardware, created ex-professo for mining bitcoins, difficulty has climbed so high that it's not profitable to mine them in anything but an ASIC (if you can afford it). Anything else and you'll lose money or barely pay the electricity consumption.

Plus, it's definitely NOT recommended to do mining on a laptop - having either the GPU or the CPU running at 100% the whole day long produces a lot of heat and will significantly reduce the life-span of components. 

Having said that, if just for fun, you could try mining Primecoin, Protoshares or Quarkcoin some hours a day - they're minable only with CPU (for now). Or better yet: mine a scrypt-based with your graphic card (it's usually much more profitable). Maybe mine dogecoins for 3-4 hours a day - Dogecoin and the dog meme are fun :)

Just don't expect you'll get a lot of any coin mining partial-time.