Both MSN and Ask Jeeves have announced that they're going to spend money on TV to try and grab some search market share. Yahoo! has been spending (on TV, outdoor, etc.) for some time on search (and local). Several surveys have confirmed a tightening of the market in terms of usage (Kelsey Group data show that most people use "two or three" engines), but Google remains the leader, with Yahoo! in second position.
Despite its spending, Yahoo! has not be able to grab the lead from Google, which has famously spent nothing to market itself (though that will change soon). The Keynote data suggests that actual functionality is what has helped Yahoo! improve its position. (Of course, ad spending can drive awareness of functionality.)
Many argue that there's little difference in quality among the results offered by the major engines (AOL search is largely based on Google results). The logic goes that it's brand equity preserving Google's market position. That would argue in favor of some sort of mass market branding to make a splash.
But when users show up, there must be a differentiated experience to make them come back. Ironically, I think Ask Jeeves is in a better position in that category than MSN, although MSN has a stronger market position.
There's also the ROI question: Does the spending€"and MSN has said it will spend "millions"€"deliver a commensurate return? In the DA world, "dial-around" numbers (e.g., 1800-CALLATT) largely generate use when they're in the public eye vis-a-vis some expensive ad campaign. In other words, there's a short-term usage bump that doesn't translate into repeat business.
If there's an analogy . . . sustained national TV spending (which might be required to move the needle) by search engines will erode margins€"more quickly for Jeeves than for MSN.