I believe they made their intentions clear: they no longer needed low-ranked members, and would retire more senior accounts as they dropped out.
It's also the fact as time goes on, more and more full members come into existence, and it gets more crowded at the top. This means there's an abundance of spammers at ranks like full member. I'm guessing in a year or two, sig campaigns below hero member will pay like faucets.
I had read that admin is working at some new ranking system, to reward the oldest people, soo signatures may follow the trend and force or just accept high accounts ranks, being at some already senior and above, soon or later they will be working with hero and legendary just. One thing is well know achieve full member ranks its just 4 months reach legendary its almost 3 years, but there are several hero as senior members already, and few legendary.
As Time goes on, the average rank will go up and up. It used to be full member, but now it's senior member. Almost everyone is senior member. Won't be long until campaigns only accept Heroes and up.
P.s. Whered you hear that?