I am looking into buying some web space, but i'm concerned about the fact that if you go over the limit they charge 2$ per gig. (i'm looking at ipowerweb btw, which gives 30 gigs of transfer per month). Is it possible for external users to abuse the web space and make your transfer skyrocket and you have to pay for it? Is there anyway to stop something like that from happening?

Thanks!

Yes it is very possible and a common problem. This mostly occurs with images, flash files, and other such media content. An example would be a highly visited game site embedding screenshots you have on your server in their webpage, without copying the screenshots to their own space. While this particular example still leaves you with some benefit (at least the bandwidth is being used to advertise your game), there are people out there that have the nerve to steal content directly off your server and use it for their own benefits (this tends to be a problem if you have a website that has images that could be useful to other people, such as a photo of a dolphin or screenshot of Half Life 2). People on forums tend to do this very often. The better webhosts have controls panels which allow you to block external linking to file extensions of certain types. You can also use .htaccess files to accomplish this if your host supports them.

Your host should also allow you to cap your bandwidth so that if it goes over a certain amount (the maximum you are willing to pay to keep your site up) then the site shuts down. This is a very good safety feature to prevent the unlikely but possible occurance where for whatever reason, your site ends up using hundreds of gigs of bandwidth. Don't make this cap too low, especially if you believe your site could legitimately exceed bandwidth usuage by a large amount. The last thing you want to do is lock up the site when you are getting a tonne of real visitors who are downloading and buying your game.

Thanks for the reply, but I was kind of thinking more along the lines of someone having a script that reloads your page over and over again into infinity just to be an idiot. Is there any way to stop abuses like this?

Denial of service attacks like that are much harder to block against. If this is a serious concern, I would recommend speaking to your host and seeing how they handle such problems. The bandwidth cap I mentioned in the above post (I edited it, now it's a paragraph longer) would minimize the damages incurred. Much like you can only do so much to prevent someone from egging your house, you can only do so much to prevent malicious users from hurting your site.

If you monitor bandwidth use regularly you could block off an IP address when you notice it's causing a huge spike. Implementing this automatically is more complicated and while I have never attempted to write such a script, I don't believe the benefits would be worth the extra load on the server.