The suicide bombers in Brussels detonated before the security check. There are crowds as you approach security checks in the Bali airport, so the same sort of problem could happen.
I don't agree ronb...you cannot enter Bali/Jakarta's departure hall without a ticket/boarding pass and all bags are x-rayed just inside the entrance door before approaching the check-in counter.
In many other airports, like Brussels, anyone can enter the departure hall and the security check is done after the check-in counter.
I believe they have changed that procedure already.