LeeAnn Prescott at Hitwise reports that traffic to Google Calendar recently surpassed MSN Calendar and is set to surpass Yahoo Calendar in the next few weeks or months. Google Calendar's traffic has grown 333 percent since April 2006.
But what's most interesting about Prescott's numbers is the fact that most MSN and Yahoo Calendar users come from other MSN and Yahoo services, whereas Google Calendar receives much less traffic from Google services.
For example, 88 percent of upstream traffic to MSN Calendar comes from Hotmail, and Yahoo Calendar received 48 percent of its traffic from Yahoo Mail or Yahoo Address Book.
Google Calendar, meanwhile, receives 19 percent of its upstream traffic from Gmail and 42 percent from Google search. Yahoo Mail was Google Calendar's third-largest source of traffic, with 2.7 percent of upstream visits, and Hotmail was sixth at 1.2 percent of visits.
Prescott says these numbers indicate that Google Calendar is cross-platform popular: Even if you use Yahoo Mail or Hotmail, you go off the reservation to use Google Calendar.
I'd go one step further with that: Whereas Yahoo and MSN still rely on a portal strategy--be all things to all people--Google relies on a best-of-breed strategy that doesn't rely on multiproduct integration. Like Eric Schmidt said at SES last year, integration comes after adoption. Why build an intricately conjoined product if no one will use it. (In the case of Google Calendar, integration is already here, but that's beside the point.)
Another big point: As I've said before (and others have too), Google has a "points of entry" philosophy to capturing users on the Web. Just like a magazine designer creates a page layout with multiple objects that attract the eye, Google provides Web services--and advertises those services--independently. Each one attracts a few eyeballs. Hence the "product tips" on Google's SERPs.