An incident in Seattle, Washington is an unfortunate example of ineffective security.
Check out this video for more on the story.
In this case, the three security officers shown in the video reportedly work for a private company who has a contract with the transit authority there to provide security. Their job is to observe and report...not to take action.
That's all well and good and probably makes some legal staff feel all warm and fuzzy, but why bother? It's certainly not security so why call it that.
All too often businesses (and municipalities) do this so they can give the public (and their own employees) the appearance of caring about the safety and security of both people and property. If they truly cared, they'd have professional security personnel (not the $10 an hour fast food rejects so often seen) working and give them authority to actually do something useful. In the case mentioned above, that would be to intervene and stop the attack altogether.
Here's some free advice to companies who are just going through the motions when it comes to security: Stop! Get serious about it before it blows up in your face and costs you far more (both financial and image) than you can imagine.