  Boyajian's Star (KIC 8462852) undergoes mysterious, irregular eclipses that
aren't yet explained. It also appears to have dimmed over a time of several
years, possibly decades. I show that Kepler's detection of a phenomenon with a
duration of t_anom is only expected if it occurs at a mean rate of >~ 30
Gyr^(-1) (t_anom / 100 yr)^(-1) for each Kepler target and K2 star. If true,
the phenomenon occurs hundreds of times during the lifespan of its host stars.
Obscuration by the interstellar medium remains a plausible explanation, since
it doesn't actually affect the host star. An intervening cloud is consistent
with the lack of an observed submillimeter excess but would be abnormally
dilute.
