I usually designate a zoo and/or statute garden as a room, so it can function as a meeting hall: migrants will path there, parties will be held, etc. Is there any reason to designate more than one? Any reason not to?
My animals are always penned away, so there's no risk of death by duck-bite from an overcrowded meeting space.
Advantages to multiple meeting halls:
1) Your dwarves will be more spread out in case of emergency/lever pulling/ new work to do.
2) Your dwarves won't make friends with each other as fast, and may form friend groups that don't interact much depending on how your workshops/bedrooms are laid out. This is a good thing
3) Traffic. A meeting hall with a one tile exit can be a bottleneck for traffic if everyone has to get in and out at the same time.
4) Quarantine. Deadly blood is contained to one meeting hall at a time, and worst case scenario you can brick everyone in and then take the time to flush it with magma.
Disadvantages:
1) Setting up all these meeting halls and making them all expensive and lush is pretty time-consuming.
Personally I have well meeting hall and an enormous dining room and several smaller dining rooms spread around the fort so that dwarves with extremely limited remits can live in small burrows.
One situation I can think of is, for example, if you have your main fortress near the surface with a bunch of magma furnaces near the magma sea.
You can put a meeting hall in both areas, so that some dwarves will idle near the smelters to haul your finished goods up or refill the ore stockpiles without needing to walk all the way down first.
