As of 5/2011 the google documentation for c2dm says this:
“Google limits the number of messages a sender sends in aggregate, and the number of messages a sender sends to a specific device”
What is the specific limitation? If my server sends 10 messages a day to 10,000 devices will Google shut my app down?
The specific limitation is derived per account and is modifiable upon (reasonable) request. For example, I have c2dm account which is “restricted” to “just” 100,000 c2dm messages per day.