[massaman_yams]

Gmail is subject to specific targeting by spammers in a way that fastmail is not. The returns for spending weeks or months finding a niche way through Gmail's filters are justified by the number of gmail addresses that can be targeted, which is probably 3 orders of magnitude larger than the total number of fastmail subscribers.

[Semaphor]

Good point, though it's still in favor of fastmail (which, as a paid service, will always be several magnitudes lower in users)