Many people are being drawn to a particular project on kickstarter rather than the brand as a whole. Given that it doesn't seem unusual.

It actually seems quite high, assuming participation follows a power law [1] distribution curve.

Take, for example, the recurrence of a given individual's contributions to open source projects - many have not contributed, but I'd bet quite a few only do so once.

[1] http://en.wikipedia.org/wiki/Power_law