This is typically not a repeat service. Users will search and find it when they need it, use it once and forget about it for 6-12 months until their mailbox fills up again. Somehow we want to convey "simple", "trustworthy", "no hassles".
The audience is purely web-based. There is no print or offline use possible for this service.
The audience is very international. More than 50% of users are not from native-English speaking countries.
This service may be made available to all users in a specific domain. The domain administrator will make it available from a menu in Gmail. In this scenario, it would be useful for the logo to be easily described by voice or email, as in "When I clicked there was that red picture of a gnu and then .."
The audience is very broad. Its is all users: young, old, male, female. Obviously they are heavy email users, and thus do skew towards more technically adept. However part of the appeal of the product is its simplicity. The technical users often recommend it to their non-technical friends.