Criteria for earning gold badges on Majesty

If you go to DNA sequences in the Animus menu it will say that memory is complete. (Like you mentioned.) Other than that, there are no rewards, not even an achievement.

If you want to tidy up though, it might give you a sense of accomplishment to get 'em all.

I've had this problem before too, never really looked into how to solve it, but now that I think about it.

Wiping the application data for words with friends (Settings -> Applications -> Manage Applications -> Words Free -> Clear Data), then starting the application again (requiring you to log in since you wiped the data) should refresh your game.

As I was typing the above I saw that there's a "clear cache" button below the "clear data" button. That might solve the issue too. Clearing the cache would empty what is there and force a refresh from the servers. If clearing the cache doesn't work, the the paragraph above should solve the problem.