msn for Mac hasn't been updated in years and doesn't support webcams
Yahoo is compatable with mac, so you should be able to cam
You can also use third-party MSN clients which connect to MSN, like aMSN and Kompote
Skype will also work with a mac but.....
...mac's don't seem to support many webcams. My old cam worked on my mac (using another 3rd party program) but my newer one didnt.
Get a PC and a mac
That's what I do lol