But why should checkin areas be more protected than any bakery, bus stop or supermarket, any place where people gather. One can't (and shouldn't) put policemen at every corner of every street.

And of course not just in airports. Train stations, buses, markets, theatres, concerts (Balaclan), anything you have in city life where people gather together.

Metros and mass transit are generally the most lucrative target, as we see here, and as we saw in London 10 years ago.

Only place I've seen some security checks was at Ben Gurion airport in Tel Aviv, where there was a mild security check when entering the airport.

This consisted of a small interview on what I've been doing in Israel, where I am going to, with whom and who packed my stuff. This all was before even entering the actual terminal building.

I see Europe in the future adopting many of the (some call paranoid) security measure of Israel. For example security checks before entering all malls.

In Paris, there are security checks at entrances to malls and big stores now.

Yeah I don't think this is easily mitigated short of increasing throughput through check in / security so that you never have large groups of people standing around.

I traveled through Baku airport in Azerbaijan last summer which had body and luggage scanners at the entrance to the terminal. I wonder how long before this becomes the norm?

This really won't help the issue. You still create choke points where many people are waiting to pass through the security check.

People interested in killing others will just go for the easiest place, so they will just bomb the line at the scanners entering the terminal.

I talk to a lot of frequent fliers, and almost every one of them has said that there is no point to a terrorist trying to bomb a plane any more. The easiest target for terrorism is simply the insecure portion of an airport. We saw this today in Brussels.