I still have to understand how to use them... But I've seen many like llamas, so i use to give out them to a new watcher or someone whose work I like, as a form of appreciation, since I cannot give points or so.
I like llamas a lot! Saying "thanks for the fav" feels like spam, so I give llamas instead to show that I appreciate the support.
It's just... I don't get why people take the time to write a comment thanking me for one and not give one back... xD I'd rather they just give the llama instead of commenting, lol! And I really want more of them... I've been a Ninja Llama forever. D:
I dunno, I kind of find them insulting, depending on who gives them.
To me they say "I didn't feel like watching or faving you, and frankly, I didn't have the time to simply write a 'Thank you', so I'm doing the minimal effort to let you know I was here." Hell, I'd even prefer the "Thx for the fave!"
I use them as a way to give a little nod to people that have favorited my work or something similar without any sort of obtrusive thanks on their page, but half of that is also so I can know if I've interacted with that person before, since I'm terrible at remembering people. :'D