It’s wonderful to see a lot of our users taking us up on our offer to merge our Blogger Profile with the Google+ Profile. For developers this means that there is one small wrinkle to worry about - the format of the ProfileId for these migrated users has changed.
ProfileId
What’s a ProfileId, and what’s it used for?
The ProfileId is a component of the path for the Retrieving a List of Blogs Blogger GData protocol call, which can either be the value default, which is the recommended value and means the currently authenticated user, or alternatively it can be the profile identifier of the current authenticated user. Up until now, the profile identifier has always been numeric, but for the converted Google+ Profile Blogger users, this is no longer the case.
default
For users that have converted to using Google+ Profiles on Blogger, the ProfileId can be derived as follows. Take the Google+ profile url for a user that has chosen to convert, for example https://plus.google.com/114895967455102275039/, then take the numeric portion at the end of the URL, prepend it with a g, and like magic, you have the new Blogger ProfileId.
If you have any questions, please do not hesitate to ask on the Blogger Developers group, and if you are on Google+, have a look at our Blogger Google+ Page.