The whole Sinai is a powder keg right now. Various MB factions are fighting the Egyptian Army there and they are winning. Israel is watching and getting ready, but won't interfere without being asked - unless the Suez Canal falls into the wrong hands.
As far as this kidnapping goes - the problem is who. The MB is not a single organization. Not that any of them are particularly pleasant - jihadis, fundies and AQ puppets, most of them.