Is it possible to use msn live messenger on a new macbook?
Do you recommend if it is possible... or is it a recipe for disaster with viruses...etc?

Yes it is possible. If it's the program you prefer then use it. It won't be a recipe for disaster with viruses, and should work quite well for you. However if you are looking for an alternative, check out Adium.

use pidgin or something

About which client to use:
-it is possible to use a native microsoft messenger for mac;
-looking for pidgin, i found that the equivalent for the mac is named Adium. This client i personally use and i am happy with it.
-For MSN chatting specific it can be fun to try Mercury ( This client has a lot of features the ms one has and some more.

About virusses:
I never have them,
Personally i think that is a matter of not opening strange links or files you recieve from unknown or known people who are infected with some message sending virus.

My experience is based on a mac with an intel processor.

Yes you can use MSN on a mac, but it is not the same as using it on a PC, some things don't work properly.

there are other good Live Messengers, such as pidgin that are pretty much the same as MSN (Windows Live Messenger)