When Yahoo bought flickr within sometime they made sure all Yahoo users can login to Flickr
Now since they have bought del.icio.us too or rather
I hope this process will continue
Even Google first released Orkut as an indiviual service & then integrated it to Google Accounts
When Google Acquried Writely Blogger etc even they integrated that to Google Accounts
One Big Question is When will we be able to Login to Youtube using your Google Account?