In all my years of using deviantart, I never actually knew what the purpose of llama badges were. I figured they're just like... a cute thing? People like llamas?
I got one today, and decided to try to google them again. Mostly, the answers are "they are a cute thing that people like" but I also found a poll where people were answering the question "why do you give llama badges." That was the first helpful answer I got-- most people said it was for fellow artist appreciation. (The second response was to get a llama badge in return.)
So, I guess you can give out one llama badge per user, and it doesn't take away from your "stash" of llama badges that have been given to you. Some people collect llama badges, or buy accessories for them, and the more you have the more your llama "levels up" I guess?
Anywho, I went back and decided to give llama badges to people who gave me some in the past, since it seems courteous, and will try to return llama badges in the future. I don't think I'll be super into them, but if folks were nice enough to bestow llama upon me then seems legit that I should return the favor.