At Google I/O this year I learned about Pull Queues, now available on App Engine. During the session it occurred to me that this might be an alternative method to gathering counter statistics without using a sharding counter. Just send your stats to a Pull Queue and let another periodic task aggregate and store the data where it belongs.
Clearly the appropriateness of this depends on your application, but it seems to me that statistics gathering would be suitable.
Okay, so I’ll have to try it out, see how it works, and post some code!