Hello
I have small idea - special page in profile, where user can observe they milestones for using trakt.tv.
Milestones would be like:
- watched 100 episodes,
- watched 1000 episodes,
- watched 150 movies,
- watched 30 comedies,
- watched whole [eg. Marvel Cinematic Universe] list,
- spend 100 hours watching shows,
- spend one month watching tv shows,
- started watching [eg. The Big Bang Theory]
- finished series: [eg. Strike Back]
- created first list,
- added 100 items to Watchlist,
- friended 10 users,
- had VIP account for 6 months.

It could be also place for some Easter Eggs, eg:
- watched Hobbit before watching Lord Of the Rings,
- girlfrieend make you watched whole Twilight series

It could be nice place to connect with social media - twitter/facebook to allow users to share they milestone (personally I think that some people would be more interested to share milestones than single episodes - more shares - more people will hear about Trakt).

It could be VIP feature.
Of course it would be quite big feature, but I think that basic milestones (like in first section) could be done quite simple.

Greeting
Piotrek - franiis
(sorry for bad English)