have both Yahoo! e-mail and Gmail accounts and a Comcast personal e-mail account—all of which I use for slightly different purposes. But I've started to notice that in Gmails where addresses appear, "Map This" links are showing up in the right column above the sponsored links.
It's a useful integration if, for example, someone provides an address as part of a party invitation (as happened several times over the holidays). It also makes users more aware of the ads to the right. And it probably also makes them somewhat more inclined to (over time) start clicking on those links—making that inventory more valuable, although it's contextual rather than search.
But it's more than just addresses; here's what Google has to say about it.