Earlier quoted context omitted.
Here is a list: http://en.wikipedia.org/wiki/List_of_generic_and_genericized...
Operative section of GP's comment: > because they merely allowed another company with a similar name to exist reason for genericization: > lost legal protection as trademarks by becoming the common name of the relevant product or service
So, MartinCron's claim is perhaps not invalidated by the list, since those names have the additional property of having become popular, but how does that technicality translate to whether or not SEOMoz needed to take action? Is the idea that it is OK for SEOMoz to do nothing under the assumption that Doz will never become popular?
By the way, I'm in no way siding with SEOMoz here -- I don't think it's clear that they deserved to get that mark (with the Mozilla confusion) in the first place, or that Doz is confusingly similar, but if they feel it is confusingly similar I don't see how you can argue that they can sit back and do nothing without having a risk of losing the mark.
Edit: Or, is your point perhaps that "Doz" and "Moz" are different words, so even popularization of "Doz" would not cause the "Moz" mark to be diluted?