Just came across the ajaxian post about smushit.com which was presented at The Ajax Experience by Stoyan Stefanov and Nicole Sullivan. It’s a nifty tool that optimizes images on any web page you pass it by using doing lossless compression or stripping out image meta tags.
I had a little fun with this tool running it on Google.com and Yahoo.com. (Just ignore any png compatibility issues and caching while you read the following… 
)
Google.com has 1 image and SmushIt reports it can be compressed 507 bytes (5.92% savings!) by converting it to a png. Assuming a very conservative 200 million requests a month on google.com alone that’s a savings of … if my math is correct … 100 gigs of bandwidth!
Yahoo.com could save even more, 8310 bytes (12.04% savings). Using the same numbers above that’s 1,547 gigs of bandwidth in the US alone!