The Washington Post polled 290 Twitter users to find out what it meant when they Favorited a tweet. Some people had more than one answer, so there were more responses than users polled. Here's what they came up with:

If the tweet was...

  • informational: 58 users favorited
  • topically relevant: 32 users favorited
  • relevant multimedia: 23 users favorited

The writer of the tweet affected favoriting also. If the tweet was...

  • from a special person: 31 users favorited
  • from a celebrity: 11 users favorited. 
  • from a friend or lover: 5 users favorited
  • from a family member: 3 users favorited 

Obviously, just liking the subject matter of the tweet was important also. If the user liked the tweet, 206 (the vast majority) would favorite it. Surprisingly, only 14 users would favorite the tweet if they were mentioned in it or the recipient of the tweet. Only 44 people would favorite as a form of unwritten communication.

Future use also determined favoriting... 

  • To bookmark the content of the tweet : 75 users favorited
  • To use the content in the future: 52 users favorited 
  • For the memory: 19 users favorited
  • For encoding: one lone user

You can check out the awesome infographic here and the full study here. I'm still partial to the hate-favorite.