Forget simply IMing or emailing your friends videos to watch. Now, with SeeToo.com, instantly send anyone video of any size, which you can both watch simultaneously, while cracking jokes at whoever it is you’re helping to humiliate.

SeeToo accepts videos “captured using digital cameras, camcorders, webcams, cellular phones or from the web” and, using their freely-downloadable technology, streams them to your friends. And they don’t have to download anything to see the video. (Though if you want to send a video, you do.)

You can also send private video invitations, which doesn’t leave your videos on any public servers. Currently, the service is only available for PCs, though Mac capabilities should be enabled within the next few months. (Hint: Using some PC emulating software, such as VMware, Mac users should be able to access the service now.)

First of all, this is not a YouTube killer. Since SeeToo plays files off your computer, instead of posting them to a publicly accessible hosting Site, it serves a different purpose than the mass-audience option of YouTube. Also, you can’t always synchronize video watching times, which YouTube doesn’t require. That said, I see a number of applicable uses coming out of this Site.

Obviously, people will use SeeToo to pass along videos of guy’s catching their nuts on fire, or whatever. Being able to get your friend’s reaction to a video you’re both watching, at the same time, definitely enhances the Internet video experience. It can also be used to prank your friends into watching something they wouldn’t ordinarily want to see (think “2 Girls 1 Cup”).

But my bet is on porn. (My bet is always on porn, by the way.) Too many guys know how difficult it can be to convince your girlfriend to participate in a Boogie Nights reenactment, which they already know will be on YouPorn.com the second you break up.

As a compromise let her upload the video on her computer, so she can send you the video on SeeToo, whenever she wants to get cheeky. That way you still get to tape the act, and she gets to use it to her coy advantage, which girls seem to like. If you’re dating long distance, or keeping contact with a girl you met abroad, watching videos together can make the lonely months fly by faster.

Regardless of what you use it for, SeeToo definitely makes showing videos, especially large-file videos, to your friends, that would otherwise stay trapped on your machine–or her machine, whatever the case may be–easier to watch.