I just got a message saying this, and Ive been on adsense for over 10 years and this is the first time Ive heard of this. Should I verify my website or just leave it as is?
Set up site authorization
Protect your AdSense account from serving ads on unauthorized traffic by declaring domains you want to monetize.
Site authorization lets you specify your verified sites as the only sites that are permitted to use your Google ad code. Any ad requests coming from sites that haven't been verified in your account will not accrue any earnings. If you're particularly concerned about malicious use of your ad code by others, you might want to use this feature as a precaution.
In addition to protecting your account, setting up site authorization also allows us to show more relevant information elsewhere in your account.