I'm looking at different mobile analytics packages and most of them seem to do http requests back to the analytics server from the server that is delivering the content to the mobile. This seems strange and I don't understand why an image isn't just served up to the mobile which points back to the analytics server with all the data required encoded into the url.
For example google analytics does this:
Serve an image which points back to your content server with a url like: /ga.jsp?&utmr=REFEERER&utmp=PATH&utmac=ACCOUNT
Then the ga.jsp file requests an image on the google server with a url like: http://www.google-analytics.com/__utm.gif?utmhn=DOMAIN_NAME&utmr=REFERER&utmp=PATH&utmac=ACCOUNT&utmvid=VISITOR_ID&utmip=IP_ADDRESS and it also writes a 1x1 transparent gif back to the client.
Admob analytics does something similar except it does a request back to the admob analytics server before it even renders out the tracking image.
Can anyone explain the reasoning behind this?