the sad truth is they are more likely to search old, helpless grandmothers than someone who looks middle-eastern, because they are afraid of being called racist, being sued
While that may be true in the US, I don't believe it is in Europe. It certainly isn't in Israel. Fourpak's initial comments were still absurd.
As for the searches in the US go, as I understand it there is a random chance for your ticket to be flagged "search this passenger", in which case you get searched no matter what. Screeners can also choose to search anyone they want for any reason at all.
I seriously doubt the random flag is useful at all though, and it certainly creates situations that are absurd (e.g. the grandmother or a small child (yes, the latter happened; the father had to threaten to call authorities and charge child molestation if the screeners didn't allow him to be present)).