I really think there is no need to scare people right now about pbmining if is or not a ponzi, there is not enough information or actions to believe a ponzi for now.
I'm mining about 6 months and NEVER but NEVER the replied to me an email, and I do not think they will do now. For now I receive payment normally, what will happen in the future nobody knows.
My guess about pbmining is that it is just a amateur canadience man or maybe two, which handles all the administration of the site.
Everyone knows that PBmining never was a formal business with public data and no one knows where are these 4284 TH/s of your power.
All we know and gives some confidence is ebay account they have:
http://www.ebay.com/usr/pbminingI leave a very interesting article that supposedly has information about PBmining and appears a name "Jeremy Biggs", it is the maximum I could find about PBmining:
http://cointelegraph.com/news/112226/pb-miningwould be nice if some Canadian in the forum provide information about PBmining or "Jeremy Biggs".