Plenty of meme juice now being given to Hitwise General Manager of Global Research Bill Tancer's list of Top 20 Google Domains. Bill explains that the table he's used to illustrate Hitwise's findings (and which I've reproduced at the top of this post) specifies "the percentage market share that each property accounts for in relation to all visits to the top 20 Google Domains."
Putting aside the often overlooked fact that Hitwise's ISP-level Web traffic measurement activities are far from ubiquitous, I sense a fallacy of assumptions in the very low numbers Hitwise's Top 20 Global Domains notes for Google Talk.
I cannot accept the presumption that, as shown above, 1/1000 of all visits to Google Domains are to Google Talk, the service. This is because that statistic doesn't tell me about Google Talk use. It simply illustrates the presumed percentage of visits to the parent Google site for Google Talk information.
Once you download and install Google Talk, your activity will be through the Google Talk client, not the site itself. You won't need to go to the Google site as you would to search for news, images, video, or other material that actually involves a query you submit to a Google subdomain URL.