I'm also in the Chicago market and am still outraged at how Infinity dropped a quality oldies station that had held up well in the market (it consistently finished in or near the top 10). I'm only 26, but appreciated the music that WJMK-FM played and how it was presented (legendary jocks, community involvement).
But the Infinity suits in New York decided their bottom line is more important than their loyal listeners (the former oldies station even had a Loyal Listener club; the irony!) and up and switched to the Jack FM format one Friday afternoon without even a hint given to any of the air talent or station personnel; some of the jocks had radio histories that went back 40 years or more.
The only reason they switched to this format is that it's a money-maker. They don't have to pay talent, they don't even have a program director at most of the Jack stations! Plus, the production work (sweeps, promos, etc.) is all produced nationally, further reducing the production costs and ending up with a thankless format that put many radio legends out on their butts. The final product is something I could hear by picking up an Ipod; there's no local flavor or anything special on the Jack stations.
Call me old-fashioned, but hearing a DJ between songs and listening to a radio station that is always holding remotes (I enjoy going to remotes) is what keeps me tuned into stations that put the listener first. Besides, when the airwaves were first opened up to public broadcasts, the government expressed that material sent over the airwaves was to be in the public's interest.