Israel has forbidden soldiers from using social networking sites (like Facebook) while on active duty. This includes access via PCs or smart phones. This is to prevent information on current or planned operations getting to terrorists. These leaks have occurred several times already. For example, earlier this year, an Israeli soldier was court martialed (and got ten days in jail) for reporting an upcoming raid on his Facebook page. The soldier had casually mentioned that his unit was going to conduct a raid in the West Bank, to arrest some Palestinians believed planning a terrorist attack on Israel. Another soldier who saw the Facebook posting, alerted the army, and the raid was called off.
The army has encountered this problem before, and constantly reminds soldiers to think twice before they post any military related items on the Internet. To that end, the military released information about the soldier who got convicted, emphasizing the punishment angle. Just another reminder for the troops.
For a long time the Israelis felt they couldn't ban troops from using social networking sites, mainly because most of them are reservists called up for a short period of active duty. Instead, the army just kept reminding everyone that only they can avoid accidents on the information highway. But this has not worked, so a total ban, while on duty, will be attempted. This will be difficult, as for many people, social networks like Facebook are an addiction.