AdSense is a direct-response advertising medium. To use Google's own words, the desired result is a "sale or other business action." That can mean anything from an immediate purchase (such as a hotel booking) to a request for more information (which is likely to be the case with big-ticket products and services).
Forget the notion that big companies are concerned only with "branding." If that were true, big companies wouldn't be spending billions of dollars a year on direct-response advertising and direct mail. Existing PPC advertising is a drop in the bucket compared to offline direct-response advertising. (If you don't believe that, see the statistics that I quoted in an earlier post.) One would have to be very naive to think that Google doesn't want a piece of the "big company" direct-response market. But if Google does want a piece of that market, it needs to be ruthless in rooting out sites that deter mainstream advertisers--such as the made-for-AdSense spam site that I described at the beginning of this thread.
(Side note: Discussions of ethics and philosophy are irrelevant to the real question here, which is whether Google AdSense can meet its corporate growth objectives without maintaining standards of quality that meet the expectations of media buyers and other mainstream advertising professionals.)