Does anyone know if you can trace the owner of an adsense account?
Reason I ask is someone had some work done on their site and a while later realised the adsense channel had been changed, now the person who worked on the site denies it was them, but if it could be traced that might help or prove the case.

well, adsense uses a unique pub-ID for every adsense account: pub-################

the series of #s represent the numbers which can be seen when you come to view the source of the web page where the adsense resides, and is representative of the google_ad_client for which clicks on the adsense on that page are credited.

who owns it is another matter altogether. but if the website uses a different pub-ID than what is supposedly assigned to the site owner, then it was changed and you're being duped. any clicks will thereby get credited to the publisher with the ID the page uses.

channels on the other hand are useful for reports on adsense performance. it does not affect the revenue, unlike the pub-ID wherein when changed, clicks (and the money earned from those clicks) are funneled to the owner of the pub-ID used.

the important to remember is the pub-ID. it has got to be what you are assigned with when you signed up with google adsense. channels can be changed as much as needed to present a desired performance report.