Trevor Lyman is well within his legal rights to email those that signed up for his email list with just about anything (exceptions are obscenities, etc), as long as he allows them to unsubscribe, which he does.
And btw, the blimp was a side note in the email.
It is unethical and disgusting, and possibly violates Google's TOS. So how much are you getting paid to pimp the blimp? You seem to be one of those people that joined only to promote the blimp.

