Heres a short list of a few tgp's that skim to trades
http://www.boneprone.com
http://www.madthumbs.com
http://www.gigagalleries.com
http://www.thumbzilla.com
http://www.88by88.com
http://www.pichunter.com
Id have to say there are some people making alot of money off skim traffic sites.
Getting bookmarkers has little to do with IF you skim but more to do with how much you skim, who you skim to and possibly most importantly the quality of your galleries. If you have a very high clicks to trades youre probably not going to get alot of bookmarkers. If you skim to traffic trades with pop-ups, trojans, browser exploits, etc... youre probably not going to get alot of bookmarkers. If youre galleries arent high quality or if you just throw a bunch of fhg's you probably arent going to get alot of bookmarkers.
Skimming traffic and trading traffic doesnt guarantee a successful site. Especially if you have no traffic of your own to send to the site to feed your trades to start with. You will likely only get a trickle of visitors from galleries and it takes time to build up trades using only that traffic source.