I've inserted your library in my ios project (using your quickstart guide).
The library work without problem in the simulator, but when I compile for the iPhone (ios 5.1) it gave me this error:
addthisios-0.2.0/AddThis/libAddThis.a, file is universal but does not contain a(n) armv6 slice for architecture armv6
I've included all the framework (except for the Social.Framework that there isn't in the sdk that I'm currently using, the 4.3.3)
How can I solve this problem?