Proposed design pattern -- autohide viewed items

I'm sure this has been implemented in some fashion, but I'd like to see more sites that have a large amount of browsable content give users the option to auto-hide what they've already seen.

At least three times this week I've had to browse sites (ThemeForest, istockphoto) with a huge amount of content where I may not know exactly what I want, but I'll know it when I see it.

The problem is that, if I go through multiple sessions of browsing content, I often forget where I stopped browsing. Or I keep seeing items that I've already viewed.

I really wish these sites would give me a checkbox to not show anything I've looked at. It would give me a pretty convenient way to look through your entire inventory over a period of a few days without wasting time. It would also help me notice new content without it getting lost in the shuffle.

So if you've got a data heavy site that users are likely to browse, consider adopting this. Let's hope it spreads on.