guys, if you are like me and have a lot of unused keys sitting in your Humble Bundle Library, then I would suggest you to just check if they are still there. I wanted to try out Tropico 3 and tried to enter my humble bundle key in to Steam, but it gave an error saying it was already used. I then looked at some other bundles I bought from Humble. Looks like almost all bundles which gave steam keys directly are all claimed by someone. I did not go through my entire library, but I know I lost at least 15-20 games now. I guess if I go through all the bundles one by one, it will probably be close to 40+ games.
Most of the games were shitty indie games, so not a big deal. Also, most of them can still be downloaded directly from Humble. But the big-time bundles like EA bundle, Paradox bundle etc are all gone.
I googled a little bit on this and it seems this has happened to a lot of people. There are posts from Jan 2014 onwards of people losing all their keys.
BTW, this does not affect the bundles which came with the new style of adding games directly to your steam account at least in my case.