The campaign runners have been getting away with lowering the rates WHILE the price of BTC has been on a downtrend since forever.
I think it's safe to say they should be raising their rates. The campaigns paying 0.010 per post or something like that, should raise to a decent 0.013 like DaDice did. The price is only getting LOWER so this is nothing but a scam at this point. Remember that things don't change as long as you keep accepting low payments, the business rulers will be happy to keep rates as low as possible without people complaining.