IMO it's worse than iAds, because there are usually paid app versions with no ads, or a way to pay .99 to get rid of them. I really don't understand why Amazon doesn't let you pay another $20 to get rid of them.
The UK models have ads too.
Have you got a link to where it states the UK? Because the laws are different here so I am at present not so sure the UK Fires will have the ads.