metadata in link titles

Idea: Once broadband is more widespread, how about some javascript (or maybe a browser add-in) that adds meta-data to the tooltip on a link? Something like the date of the last update and maybe the registrant of the link's domain when you hover over the text. I'll have to look into it.

Has anyone seen something like this? It's like Alexa, only more integrated. Speaking of which, is it common knowledge that Amazon owns Alexa now? Seems like a lot of potential for a conflict of interest there.