Sure their cap is a rolling 30 one. And their cap is higher but not by much. Their highest tier 1.5 meg has a cap of 17000 MB a month. That's still a measly 16.6 GB a month. Until sat elite companies decide to act like the big boys and spend some actual money on improvements they'll continue to suck. Verizon and AT&T each spend over $1 billion a year on FiOS/FTTH. Wild Blue/HughesNet could each launch at least 4 satellites a year for that amount of money. That would be enough to handle any capacity issues.
the problem is probably not launching a Sat. but more likely having an available geostationary orbit to put it in....and deciding if that orbit is worth using for internet VS. some other application that could make more money
Far easier to work witha rolling 30 day contract than a stupid 24 hour one. As mentioned any significant download could end up in being throttled. This is much the same as what Virgin are bringing in for their UK customers on cable, but it is only for peak times and a shorter period.
If you want to download 16Gb over a month, or 16Gb in a day thats your call, not having to spread it out.