The Yahoo! and IE7 combination is no real surprise to me because I'm sure IE had a black eye once Google started displaying the "download Firefox" link to IE users and we all know that Google started dominating over Yahoo! - Yahoo! wants to recover some of the search engine share and IE wants to recover the browser share it lost.
Personally, the only time I even think about opening up IE is when I need to test something or a site doesn't support Mozilla/Gecko for whatever reason.
And, for the not too faint of heart, you can have multiple installations of Internet Explorer. It's not recommended unless you do some heavy duty testing, but it
is possible - just download the
standalone IE packs from Evolt. The site also has previous releases of just about
every other browser out there as well.
A note about the standalone IE installs is that they may be missing some functionality that comes along with IE. The main purpose is just for testing web pages and that's all they should be used for.
If all that seems like too much, then
BrowserCam is a great alternative (one I use and can recommend).
~ Teli