Abu Abdullah, director of internal security for Hamas in Gaza, has warned of new schemes used by Israeli intelligence to gather information from Gazans.
He mentions phone calls that are set up to sound like surveys about how Gazans feel about, say, the electricity shortage, and then moving into more sensitive topics.
He also mentions that Israelis are attempting to contact Gazans through the Internet, and that Hamas is trying to monitor these attempts.
Another article talks about how the Shin Bet is using Twitter and Facebook to communicate with young Palestinian Arabs. They will gather existing information and then befriend the Palestinian Arabs to gain more intel, often by pretending to offer them employment.
All of this is quite believable. People don't realize how much personal information they give out over social networking sites, and the methods described here are often used in corporate espionage, let alone internationally.