Backup taking a lot of space after OSX update

I wasn't sure where to put this.

I have a MB Air 128GB drive. Before updating to 10.7.2 I had about 65-70GB free. After updating to 10.7.2 and iOS 5 to my iPhone and iPad, when I check my HD, it says 40GB free.

I was wondering what took up so much space so I went to About My Mac and see that for the HD space break down, Back Up is taking 30 GB. I'm assuming these are the Time Machine snapshots, but 30 GB seems like overkill.

I have a 2008 MBP that I also updated to 10.7.2 and the backup is under 1GB.

So what happened to my Air and how can I shrink the size of the backup to reclaim my space?

Thanks.

I found this article, but it doesn't tell me how to delete or limit the size:

http://support.apple.com/kb/HT4878