There's another sponsor that has 100s of FHGs and I know myself and others don't use them either. The reasons? They're crap. 98% of the people building galleries forget that their job is to try and sell something. Those that know about selling don't want 16 pics AND a 1 minute clip. They want just a pic gallery and just a MPG gallery. Not combined. TGPs list PIC galleries or MPG galleries. Where the heck are they supposed to stick "combined" galleries

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This other sponsors galleries have thumbnails on them that are so big that there's no reason for a surfer to actually spend any time on the gallery. They can practically see the full size image by looking at the thumb. If the surfer doesn't spend any time on the gallery, there's less chance of your actual ad text (if you have any) catching their attention and clicking thru.
The reason (as someone else who seems to know what they're talking about said) for 6 - 10 sec clips as opposed to 1 - 1 minute clip is so the surfer doesn't have the time to finish whacking off and goes to join the site to get the full movie.
I like FHGs as "filler" or for "fake" TGPs. But frankly, I'd be much happier being supplied with the content from the FHGs so I could build galleries that actually sell.