Really? ... I'm seeing them adopted more widely in Europe now by businesses. Perhaps as second hand or lease prices are coming down. Maybe that doesn't translate to the US ...
Quite nostalgic seeing them run around Central London with business signs on their side... much like the originals. My point: not a gimmick in my experience.
To Thunderbird, however, we can actually donate to.
Though, just because money goes to the corp, doesn't mean it will contribute to Firefox' development either.