It looks like it's getting hard to keep track of sites that are getting closed these days..
Seems like we'll be expecting new crops of PTC programs to arrive to replace them..
Well, 33bux.com has been online for many years now and I've used it a couple of times for advertising due to its cheap prices.
However I noticed today that it's gone down.. thankfully I've never purchased any huge amounts of adverting there, and I've received what I've purchased so far in terms of traffic, so it's no big deal.
As for the sites that are connected to this admin ptccentral has published a good list of them with scamming proofs here :
33bux, BuxBoss, CanadaBux, BigUsaBux and BuxLeader