Facebook don't like to step back while playing with Google and it's various services especially it's new Social Network, Google Plus. Thats why Facebook Launched Bigger Profile Images To Facebook Profile Pages after Google+ redesigned themselves and launched so many new features.
Currently, the profile photo included in Timeline is measured to be 130*125 size. In this small size, when a user clicks the photo it becomes large preview. However, as Emanuele Bartolomucci and a number of Twitter users have noticed, Facebook’s profile images now measure 166 x 160 pixels. Difference in size is shown below.
After the total redesign of Google Plus, Facebook is launching new feature including this and Uniting of Timeline URLs and Facebook Mail IDs. Of course competition between Google And Facebook is becoming tight and we could expect more features soon.