This is a fairly common practice in advertising called "roadblocking". It happens on the radio, on TV, and (as you can see) on the web.
The idea isn't to display the exact same banner (although, that will happen, from time to time), but to display three almost identical ads. Same colors, same theme, same message, etc. There are a lot of reasons why someone would want to do a roadblock, but they're mostly irrelavent to this discussion.
To expand on Jeff's Answer, we have only three ad zones. If you feel that's too many... then fine, whatever, but doing a roadblock is no more "garish" (as you put it) than not doing one. It's three ads, they're not animated, and they're relevant.