I think advertising budgets are rarely cut, and sweeps are part of that. For example, our company has cut health benefits, raises, 401k matching, bonuses, stock options, and pensions - BUT they still sponsor sporting events at the same level as they have in the past.
Personally, the last 6 months have probably been our family's best ever at sweeps (in 4 years), which just goes to show that random chance never fails to be random.
I do notice that I win less frequently at instants, but I've attributed that to being more selective in what I enter.
As far as the last couple of weeks, folks are busy this time of year and probably posting less often as they squeeze in sweeping into their holiday schedule.