With the 10.4.7 update of Mac OS X, the OS is calling back to Apple's servers periodically. There is a new process called dashboardadvisoryd with makes the tcp connections. The tech note on 10.4.7 has this entry:
You can now verify whether or not a Dashboard widget you downloaded is the same version as a widget featured on (www.apple.com) before installing it.
If this were just for this purpose, this check could have been done when installing a widget. I assume that this process is also checking the currently installed widgets to see if they are up to date. I think a better implementation would be to have a button in the area of the screen that shows all of the installed widgets, that would check for updates.
[via The Apple Blog]