I was having a similar issue on an iPhone 3G running the latest firmware prior to iOS.
When uploading only pictures I took w/ the iPhone's built in camera app, all the photos were uploaded to a folder in Picassa web labeled w/ the date of upload, not the date the picture was taken.
I didn't check to see if the pictures had their metadata changed where the date created would be changed to date uploaded, but if so, that is seriously broken.
Not sure if it is good news or not, but since I've upgraded to iOS 4, the app no longer recognizes new pictures requiring me to manually upload pictures one at a time. Might need to go back to pixel pipe.