Want to be invincible in the sky? Nowadays anyone can track your whereabouts especially while operating in public airspace. The company FlightAware.com grants users accessibility to view a wide range of flights and their scheduled routings. When an aircraft is operating in controlled airspace their identification number must be clearly visible on the fuselage. This goes for private flights too! Pilots talking to air traffic control are broadcasting their whereabouts and intentions on public radio frequencies, making it even easier to listen in on the open skies.
Aircraft owners have the option of blocking their location from being released to the public (aside from radio transmissions that the pilots may make). You can also block your tail number with the NBAA (National Business Aviation Association) which operates and maintains the BARR (Blocked Aircraft Registration request) in conjunction with the FAA. Companies and owners like to do this when they're regularly transporting high-profile passengers or travelling to controversial (or sometimes dangerous) destinations. Alternatively, private flights operated by management or charter companies may identify themselves by flight number, which can be changed trip to trip.
According to Erictric.com, Apple CEO Steve Jobs has recently requested that his tail number be blocked. Jobs currently owns a Gulfstream GV with the epic tail number N2N. Although his plane can't be tracked online, bloggers, reporters, and journalists can still always snap a photograph of his plane and quickly update his whereabouts to the internet.