Google is pushing hard to jumpstart its radio ad business, leveraging its $1.245 billion acquisition of the DMarc rep business in 2005. The search leader says it is working with 900 stations in 200 markets.

But so far, according to an article by Miguel Helft in The New York Times, its list of participating stations in major market is spotty, and the inventory it gets is almost always remnant, rather than drive-time.

Google’s Bay Area radio affiliates, for instance, are low-rated stations in outlying areas rather than metros. Its top-rated Bay Area station ranks #18. In New York, its top station is #27. One problem: Google has ramped up the paranoia by hiring away top sales reps from stations. It also had been rumored to be in talks to acquire Clear Channel, the nation’s largest chain of stations, but apparently nothing panned out with that.

Meanwhile, the Times article notes, other online ad managers, such as Bid4Spots and SWMX, are getting a flying head-start on them. They don’t have an apples-to-apples comparison, but Bid4Spots has 2,400 stations. SWMX says it has 40 percent reach. The deals are probably not exclusive.

Google’s facing similar challenges in its efforts to get into Cable TV (and maybe broadcast TV?). The article notes that Google was turned down by Comcast Spotlight, the rep arm of cable’s largest MSO, which is pushing harder than most to drive cable and online sales. Comcast recently hired Adrienne Skinner away from Centro, the Chicago-based national net for local sites.

The cable guys obviously, are always the “woulda shoulda” of local online sales. To date, there have been dozens of false starts. One way they are beginning to have an impact, however, is in joint promotional and sales deals with MSO-branded car sites (i.e. vehix.com, which is largely controlled by Comcast, and beepbeep.com, which is Time Warner).