Given the fact that Christians believe God to be all good, and Satan to be all evil, that comparison invalid. I doubt you feel, when Christians say 'I shall pray for you' or 'May God watch over you', that they are doing you a misdeed. Someone saying this is wishing you well. Unless this Satan dude they speak of is omnibenevolent, wishing that you were under the watchful eye of he who is omnimalevolent isn't a nice thing to say. But hey, you can be annoyed at your own things. :P Now if I was told "May enlightenment find you speedily" (or something like that, heh) by a Buddhist, I may be a bit annoyed, since I'm not Buddhist. But I really shouldn't be because they are wishing something good to happen to me. It's the thought that counts.