untapped revenue source for CTA?

Earlier today I was talking with a regular rider of the CTA Red Line and she mentioned something which struck me as an obvious source of new revenue for the cash-strapped agency:

On railcars and city buses the great majority of "ads" promote CTA or City of Chicago events and services. There are almost no ads for consumer products produced and sold by corporate entities.

Why not? If CTA actually sold ad space on trains and buses wouldn't that help easy their money shortage? I recall seeing large ads on the sides of buses and poster ads inside the rail cars not all that long ago. Why no more?

While selling advertising on the trains and busses may bring in some money, I doubt it's a hugely significant amount (that would have any real impact on their current budget crisis). And also, there are a lot of ads out there that aren't for the CTA or the city iself (which would probably pay for the ads like any other entity would). Maybe around this time, they're not as visible because the summer is coming up and the CTA and the city are promoting local events through the ads on trains, so there appear to be fewer ads for other businesses.

Also, my opinion on lots of advertising on public transportation is that it's just plain tacky. If I'm riding the train, I'd like decent looking facilities that are free of "SPEND MONEY!" messeges provided by local businesses. Above-the-window interior advertising has been there since the first days of streetcar advertising, and I don't really have a problem with it because it's subtle, but also noticeable. It's not like those godawful ad-wraps, which ruin the aesthetics of the trains and busses, and distract more than they advertise. Those are the types of ads that will ultimately prove futile - the money they bring in isn't a replacement for the lack of funding they're getting from the government. It's more of a temporary funding fix. In fact, the CTA could probably rent out an ad-wrap on every single car railcar it owns, and still end up in financial trouble, because there is no substitute for proper government funding.

i agree with byte in that ads make things look extremely tacky. However, when a agency is talking about massive cuts because they are so far in the hole i would think any extra revenue, from any source is good.