Google_Base is coming. Hide the children. Let me understand something... Google wants to introduce a free listing service so that anyone can put attributes-based product or services on Google's servers for free, for example "a description of a party planning service" (Craigslist) or "a listing for a used car" (eBay). Hmm. So lets run down what Google is (purportedly) looking to build - a free nationwide wifi network, a (free?) online payment system, a free online collection of published works, a free network-based OS via desktop search/toolbar, a free Office and business productivity tool offering, a free VOIP communication platform and a now a free listing service.
Pushing aggressively into multiple markets (with free products) doesn't often work, but Google has proven it's capable given its resources and growth (one perspective on this google_takes_all). That said, every action has a reaction. Getting sued by rights holders for copyright infringement, by trademark holders for not securing or paying for the Gmail mark, and by Microsoft for employee poaching is indicative of the response to (and ultimately a measurement of) the aggressiveness of Google's initial course of action.
I don't believe the general consensus that a company with Google's business model or team can be overextended. Ultimately they've created an innovation machine on the basis of a near monopolistic control of search and ad placement. Offer something for free, tie Google's brand to it and (tada) you will have some level of adoption. I would, however, point out that innovation unfettered (and made public without actually releasing anything) can sometimes equate to the proverbial stick in the hornets nest. Google seems to have lots of sticks riling up lots of hornets...
Update: This comes from Techdirt Understanding Why All Your Base May Belong To Google. Irregardless of Google using Google Base to compete with eBay/Craigslist or not, the article comments on using the Google Base structure as a simple interface to a hosted database that developers could use to build web-based applications. Essentially a developer would self-define his online database using Google Base and could push/pull that info to his app. An alternative to writing SQL queries? Now Oracle can start fretting (MS is already there).