I recently did a test on our pets. Mind you I am using the lvl 64 Pet.
I had a Enchanter and Pally help me cause we just dont have enough buffs to do it.
Our pet can hold 30+ Buffs. If I recall. I was at a friends house drinking when we tested it. I will do it again tonight and test again.
I feel innafectual now LOL pet can take all the buffs and I have to pick and choose.
I believe that it was stated somewhere that pets can hold either 32 or 36 buffs (forget which, offhand).