[Mike_M]

Yep you run the risk of being banned for life and dont even bother trying to rectify things if that happens. It's just not worth the risk.

I had a loans site and a debt management site, and as some of the keywords clash (eg 'debt consolidation'), I tried the legit way and I asked my adwords account manager for an exception to be made. No chance. I even explained that the 2 sites were offering COMPLETELY different products, which actually delivers a better google user experience.

The response was predictable - 'No' followed by a standard email explaining google's stance on double serving:

"To protect trust in Google, and to provide a quality experience for our
users and partners, the double-serving policy is strictly enforced.
Exceptions are granted only in very limited cases.

Advertisers seeking an exception to Google's double-serving policy must
contact AdWords Support who will then review both websites. In order for
an exception to be granted, both of the criteria below must be met:

The destination site for each ad offers different products or services
(for example, a large manufacturer with two product sites, one solely for
stereos and one solely for computers, both running on keyword
'electronics').

Each destination site has a different layout and design, and each URL and
domain is different."

I explained that my sites met the criteria, and was still told 'No'.

So I gave up...