[Jeremy_Reaban]

Well, they tend to be packed with people. (If they're not, they tend to go out of business). I guess they're hard for terrorists to resist.

[Travis McGee]

Grenades are cheap and available in Europe since the end of the cold war, the Balkan wars etc.

A grenade in a disco can also be the local Mafia's warning to the other clubs to "pay for protection or else".

[goodieD]

Well besides the terrorist attacks..there are the ones that simply go up in flames... I think the problem is that the overseas places overpack beyond the legal limit (if there is one). While this doesn't explain the flammability of the places, it does explain why so many die there.