In the coming weeks if you happen to notice an unusual decline to your CTR, it might be down to a new display URL policy.
AdWords recently announced on their blog that they were going to change the display URLs so that the domain portion is all in lowercase.
For example, if we were using the following as the display URL:
You do not need to go back and edit your ads, they say they this will be automatic when the ads are served.
For those who have domain names which do not need capitalization, I suspect it will not be an issue. For example, www.google.com. However those who need to highlight the actual name of their domain through capitalization will most probably take a hit to their AdWords performance.