Assuming I can put my opinion here...
I think word choice is always important.
Like and thanks are very interesting depending on what the situation is...
For ex:
"I like pink cats"
- thank you! (Finally someone agrees with me, etc.)
"I like pink cats"
- like! (This is a good message. Funny, I like it. Maybe interesting.)
I feel that since like is almost a popular button on most social sites, it may be implanted for familiarity. Obviously having a thanks button is too foreign...