Google did this last year and it's a ridiculously easy way of adding extra space if you use Drive, Picasa, or Photos. Basically, all you need to do is go to your account, scroll down to Security Checkup and click on Get Started. Once you finish the checkup (which takes all of a few seconds), the 2 gigs are added automatically.
On a related note, I just checked to see how much space I have now and I'm currently using all of 118 megabytes (or 0.61%) out of 19 gigabytes. Clearly, I needed that extra 2 gigabytes. :P