Bookdog shares the Apple URL Loading System with Safari, so if you've logged in to Google in Safari and checked "Keep me logged in on this computer", Bookdog can access Google without entering a password.
After several days studying Google's Accounts API, I was surpriesed to find that Bookdog 'just worked' without implementing anything! A few peeks into the cookie jar made it apparent what was happening, but raised some new issues. Because users can have more than one Google™ account, Bookdog checks to see which account is logged in before uploading or downloading bookmarks, and can automatically log back out and back in with a different account if required, getting the password from the Mac OS X Keychain if it had been stored there by Safari or another browser. If all else fails, of course, the user can enter the name and password into Bookdog, and if desired Bookdog can keep it in the Keychain.