Can mashups be shaped into businesses?

I see so many great examples of "mashups" -- developers combining unique data sets or applications with programming interfaces from Google, Yahoo! or others, all to create new Web services.

Adrian Holovaty's ChicagoCrime.org and Dave Pell's Rollyo fit this description nicely.

Knowing Adrian, I doubt he worries much about whether or how to commercialize ChicagoCrime. He built it because it was a great idea, and because he knew how to do it right.

I don't know Dave Pell, so I don't know if he ever intends to make big bucks off Rollyo. It, too, is a sweet little piece of search customization.

The question is, even if he or other mashup creators did want to turn their Google API- or Yahoo! API-driven concepts into going businesses, how can they do that?

I've checked terms of service for the major Web APIs from Google and Yahoo!. I am not an attorney. I don't even shop for ties in the same stores as attorneys. Nevertheless, so far in my readings, it seems only the terms for Google Maps API seem to allow commercial use, as long as the content is made available free to consumers.

And all the API terms appear to restrict, at least contractually if not technically, how many requests (1,000 seems to be the magic number) an outside site can make against each interface each day.

As I see it now, most mashup creators would have to switch to a commercial license, or replace the API calls with alternative technologies, if they ever want to make money from advertisers or consumers in any form. They'd also have to pony up if they wanted to grow beyond a modest traffic volume.

Jump in here and tell me what I'm missing, or whether I'm completely missing the point of making mashups.