In the "help us grow this site" box on the beta SE sites, there are six icons for ways to advertise the site through social media. Five of them use company icons to connect to that company - facebook, twitter, delicious, stumbleupon and linkedin. But the first icon is a gmail icon, used to represent email in general.
I don't think that's a good generic representative of email - I'd prefer something like the envelope icon we have at the left of our names in the top bar. Certainly, when I clicked it, I expected to get gmail, though my default mailto handler is actually Outlook - instead I got Outlook and was momentarily confused.
I also suspect that Google might get annoyed about it in trademark terms, but really, "one of those things is not like the others" is a bigger concern for me.