One of the many mind-boggling statistics about Facebook—300 million members, half log in daily, 8 billion minutes of use per day—is that the social network also happens to be the Web's largest photo-sharing service. By a lot. Earlier this month Flickr announced that it had received its 4 billionth upload, total; Facebook is up to 2 billion a month.

Facebook's big advantage, of course, is that it lets you tag your Facebook friends in images, sending alerts rippling throughout the social network. The interface is snappy, and integration with mobile devices like the BlackBerry and iPhone is superb. Since pretty much everyone you know is on Facebook, it has become the default place to share albums of birthday parties, vacations, and the like.

But one big drawback to Facebook photos has always been that they are shown in relatively poor resolution—about 600 by 600 pixels. That's so-so for onscreen viewing, but poor for bigger displays, HDTVs, and (especially) printing. So far, as the statistics attest, that hasn't been a big liability. But Facebook will be integrated into the next version of the Xbox Live platform, bringing the social network onto gigantic HDTVs. Microsoft gave me an early look at the feature, and photos there look OK, but not spectacular.

This mediocre image quality also limits third-party book-printing services—such as Pixable, a promising startup that lets users easily make hard- and soft-cover albums out of Facebook photos. Pixable's killer feature is that you're not limited to your own photos—it will grab any image that you'd normally have permission to see on Facebook.com. The service also automatically grabs information like tagged names, captions, "likes," and comments. It's a great concept, but the biggest printed images Pixable users can get out of Facebook's 600 x 600 limit is five by seven inches.

I spoke to Facebook's Scott Marlette, an engineer who helped invent and scale Facebook photos, about the company's plans to go high-res. Bad news: there aren't any. The site is focused on encouraging users to tag and share images, not improve how good they look.

"It's funny," Marlette says. "For me, taking pictures is more about photography—I want to see the details in the photo. But the reality is, the value of the photo is who's in it, where was it taken, and your memory or experience associated with that."

As you might expect with a company of Facebook's scale, there are technical reasons to dread going high-res, too. Doubling the width and the height of an image requires four times the data. And a bigger concern than file size, Marlette says, is the sheer number of files involved—today, each uploaded image is turned into four images of varying resolution, so 2 billion photos per month means 8 billion files.

I had been under the mistaken impression that Facebook has all along been storing an original-resolution copy of each image it receives, and was just not making it available because of concerns about blowing the roof off its already sky-high bandwidth needs. That isn't the case. In fact, for most photos, Facebook's servers never even see the original image—its uploading tool first compresses each picture file on your computer, to shorten transmission time. That means that even if Facebook does eventually add high-res support, it would work only for new uploads, not the billions of images users have already added.

Last week Flickr, which does allow for high-res uploads, added support for people-tagging. That site also supports geotagging, an increasingly popular feature that maps photos to exact GPS coordinates. Flickr won't threaten Facebook's lead in the photo department any time soon. But it's a shame that online photo sharing seems to be splitting in two directions: tolerable-and-social on Facebook versus awesome-and-less-visible on Flickr and other sites.