One way to get the same effect is to put some download -speed- limits in place. For images you want to put a relatively normal limit on it, like, max 20kb/sec (depends on size), but force it to be only 1 concurrent request. For thumbs, you want 4 concurrent requests. Also block out all user agents that are not a regular browser.
There are also apps like Strongbox that, IIRC, will see if a user is acting "weird" (e.g. being a bot
) and will temporarily block them.
Actually limiting the amount one can download is, IMO, the best way to get a surfer to charge back or not rebill. (At least, I know it pisses me off if I've found the perfect thing to download, and it won't let me due to some 3-a-day limit, makes me cranky and not interested to come back later either).
Just my 2 cents
