Kongregate was removed from Google Market, but that does not prevent it from being distributed separately (On Android you can download apps directly from the web and install them, without using the app store).
Suddenly I'm sensing a pattern...
On, uh, AT&T.
@jancona: I didn't sideload with ADB. I copied the .apk to my phone via USB and used a file manager to access my file system. Tapping on the apk installed it just fine. If AT&T disables sideloading with ADB, how do developers test their apps on AT&T's Android offering?
@lukeschlather: I'm using a Nexus One; it may not be possible for phones customized specifically by AT&T. If this is the case, it's pretty f'n unfortunate.