StumbleUpon launching site-specific Stumbling

This is weird. Last night it occurred to me that Webware should have a StumbleUpon-like feature: In other words, that there should be a button on the site that links to a random Webware review--because if you don't come to the site frequently, a write-up on a cool site we saw a month ago might be valuable to you, even if it isn't, strictly speaking, new. I also began to wonder if it wouldn't make sense for many other sites, especially blogs, to add a random-link feature to their front pages.

Then this morning I read (on Mashable) that StumbleUpon is launching a feature called "StumbleThru" that does just that. But just for a few sites.

As I write this, StumbleThru is not yet live or linked to from the StumbleUpon main site, but the StumbleThru index page is live. It shows you that you'll be able to perform site-constrained "Stumbles" on 13 services, including user-generated content sites YouTube and Flickr. The feature isn't turned on yet: right now, clicking on the sites generates an error.

I presume that the 13 sites in this feature were added based on their popularity to StumbleUpon users, but it leaves me wondering if StumbleUpon will release instructions or an API so people who run other sites will be able to put the function on their own sites. Presumably, if made available, the tool could feed popularity results back to the StumbleUpon service, and get destinations tailored to individual users.

Obviously, I think StumbleThru is a great idea. I've been waiting for this feature for 15 whole hours--enough time to work up a nice appetite for it. And now that it's almost here, I already want more of it.

Related news: it's rumored that eBay is about to acquire StumbleUpon.