People cancel HBO, but isn't it seasonal around the end of different shows?
It could be, but it's hard to tell based on the data that's publicly available. The most detailed numbers I've been able to find are quarterly figures, and those don't seem to change much.
This is what I found when I looked up the last four quarters (note that all of the numbers are for the end of the quarter):
2012 Q4: 28.7 million
2013 Q1: 28.77 million
2013 Q2: ?
2013 Q3: 28.9 million
I drop HBO when the NFL season starts because I buy the Sunday Ticket and really have no use for HBO once the football season starts. And the monthly price is pretty close to what the Ticket runs (I have DirecTV, obviously).