This article is from the Digital Broadcast Satellites FAQ, by Brian Trosko firstname.lastname@example.org with numerous contributions by others.
Maybe. The dish needs to have a clear line-of-sight to
the satellites, but the angle which the dish arm points at
isn't the angle the signal is coming from. The signal comes in
from roughly 20 degrees higher than the angle of the LNB arm.
So, even if the dish seems is pointing right at a solid object,
the signal might not be obstructed. The azimuth markings scribed
into the dish assembly do take this difference into account.
Some people who live near airports have reported transient,
momentary interruptions of signal due to aircraft flying
through the beam.
Some individuals have succeeded in getting signal through
a window. The type of glass matters enormously, with
Plexiglas being the most favorable, single-glazed much less so,
and double-glazed windows not working at all. Even if this
does work, it will knock the signal strength back dramatically,
so it should only be done when there are no other avenues to