This is more for the ladies, but...
It's legal: cops seize cell phone, impersonate owner
"In November 2009, police officers in the state of Washington seized an iPhone belonging to suspected Prohibited Subject. While the phone was in police custody, a man named Prohibited sent a text message to the device, reading, "Hey whats up dogg can you call me i need to talk to you." Suspecting that Prohibited was looking to buy Prohibited from Prohibited Topic, Detective Prohibited replied to the message, posing as Prohibited. With a series of text messages, he arranged to meet Prohibited in the parking lot of a local grocery store—where Prohibited was arrested and charged with attempted possession of Prohibited subject."
http://arstechnica.com/tech-policy/2...ersonate-owner
The full legal opinion the above article is based on can be read here: http://scholar.google.com/scholar_ca...,5&as_ylo=2012