Techcrunch has a great assessment of the Messaging War that is looming between Google, Facebook and Apple.
The recent underhanded switching of primary email addresses by Facebook is all part of this war. A calculated loss of trust in a larger war with massive spoils for the ultimate victor.
See this TechCrunch post for more information on this change and how to undo it:
Here is an interesting wrinkle on all this...
You can add additional emails to your Facebook account. You can also choose which email is shown in the your timeline. One feature gMail offers is the ability to create email aliases by appending +words to your email address. The real genius of this is that you don't need to create these addresses in advance. You can create them on the fly. This is really useful when you are signing up for different services on the Internet. By using these aliases you can get some insight in to which services are trading your email addresses. An example of these aliases is here:
So what is the point of this? If you have already set up a gMail address as an email on Facebook then the email check in the Facebook profile will not let you add an additional email alias from gMail. It must obviously be looking for the "+" sign and dropping the following text.
Facebook is obviously doing a specific test for gmail aliases because the error message is not that the email is invalid. Instead the message is that the email has already been added.
What is the bottom line? We can expect the major players to erect more and more hurdles that will will potentially inconvenience their users as this war plays out.