Season ticket sales have plummeted for the Fins. Consider this (number of season tickets, rounded):
and this year, its around 41,000
So 61,000 is the highest total (other than the slightly inflated totals) from 192-1974.
And the 41,000 is the lowest - ever.
But the trend has been downward since, basically, Dave left. I have to believe there's a combination of things going on. Ticket prices versus the economy is certainly a factor. But there is also this trend of mediocre performance, coupled with them always being on TV.
Now with the possibility of blackouts, the only way you'll be able to catch your phins is by going in person. And that's much less expensive than the Dolphins offerings: I just looked at stubhub, and found tickets to all of the games readily available. And some you can pick up now for as little as $18. Why would you buy season tickets in that case?