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.
My campaign has not changed their rates for months and I doubt they will. While it is true that bitcoin price has dropped what they pay is good enough and I will not complain. Mainly because I'm not in it to make much in the first place I just post because I would post anyway and I also play at the dice site so I wear their sig.
I can't see where you are going with scam? If they are clear in the Op that you will be paid xamount and you are paid x amount where is the scamming?

The business rulers are happy to keep rates low, because at the moment business income for start ups is low.