none! but they can do it. please see what words i use. i do not say that they do, only that they can.
Lots of things can happen through all kinds of mediums - Apple could decide to collect and redistribute personal information on iPhone users through an implicit agreement, Sun could, effective immediately, charge royalty for all Java programs produced henceforth, and the operators of Deepbit could decide to capitalize on their pool monopoly by doubling their use fee. Furthermore, the world could end tomorrow.
and people know this, and are scared of it. look at facebook, people are crying and screaming about privacy issues.
but they don't know what microsoft or apple can do with their computers. people are just ignoring/unknowing the fact that they can have access to their computers.
on this forum some people are paranoid that the governements or corporations are gonna rape them in the ass, but they still use windows or mac, not knowing what they can do if they like.
open source are not suspicious, you can read the source, and verify that it is not malicious. you can't do that with closed source.