Google would like to protect their trademark term and not have it turned into a verb for web search. I guess it makes sense to me. With Kleenex, etc. Google doesn't want to be a commodity with search. Danny has a detailed write this morning on the non-issue that has become an issue.
Overall, I think everyone knows that Google's trademark police face an uphill battle in having to send these types of letters out. But sadly, that's what the laws seems to require. I guess every three years, we can all get worked up into a state over them, despite the fact that people will keep on saying google as they please.
In the end, the letters will go out and the authors will continue to ignore them and write whatever they want to, as is their right.
Most people agree in the forums.