The example in my mind was Kongregate being removed from the Market. It got back on, but the comments from Kongregate referenced "competing app stores".
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.
https://market.android.com/details?id=com.kongregate.android...
Also, in the blog's comments you were asking if Google will allow the distribution of another App Market to be distributed via the Android Market, looks like they do:
https://market.android.com/details?id=com.appspot.swisscodem...
I could be misreading what you had posted, if so, apologies in advance.