Would you have had the same negative reaction if they had set their frequency cap set to a very conservative number?
FWIW, I'm having good results with a remarketing campaign that has the frequency cap set at three per day.
Quite possibly if it was set extremely low, almost so I didn't notice it. I'm not most people though, so I'm likely not a great person to gauge response from. For many online companies the target market is, shall we say, a bit less internet savvy than most of us.
For me, it would work a lot better if it was only shown on relevant or semi relevant pages. When I'm focused on researching green polka dot widgets, spamming me to death with red widgets isn't likely to produce the desired result. It also makes it obvious that I'm being re-targeted.
Marketing agencies will often bombard people with radio, tv, and print ads again and again so It clearly works or they wouldn't keep doing it.
The whole thing is quite ironic. Google thinks they are the internet police protecting us from spam, yet they are one of the leading retargeting spammers on the web! To me its the most insidious type of spam as it follows you from site to site.