Avrom raises the issue of security guards in the synagogue, and asks whether they are really needed because of security concerns or whether they are there just to satisfy our paranoia. He concludes that the chances of anything happening in a city like Toronto (where he lives) are remote and suggests that they stop searching regular worshippers' bags.
Perhaps because I've lived in Israel, I have no objection whatsoever to being searched on my way into shul; in today's day and age I think there is a legitimate security concern, the guards have to do what they have to do, and better safe than sorry. If anything, G-d forbid, did happen in a large synagogue, the entire community would be demanding to know why there was no security when there was such an 'obvious' threat.
I do, however, agree with Avrom that the guards stationed in front of shuls are mostly ineffective. My objection is not that they're there, but that they usually don't do a good enough job -- that they are just doing enough to give the community a false sense of security. As Avrom says, many of them don't really know what they're doing. They don't always cover all entrances. In England, shul guards are explicitely forbidden from carrying a weapon (only the police in the UK can carry guns). What's the use? On Erev Rosh Hashana I was actually scanned with a metal detector on my way into the building. What could they have done had someone actually been carrying a bomb? The false sense of security and the charade make me just as nervous.
I'm not sure what the answer is -- I'm not sure you can ever be fully protected. I do know, however, that it's time the community stopped playing games; either hire real professionals and go all-out, or admit you can't protect us.
PS. In some shuls in England, security guards often have an additional use. One famous story concerns a security guard who asked a woman entering the shul the routine question, "Madam, are you carrying a mobile phone?"
"I didn't know I was supposed to bring one!" she answered (seriously).