I used to work for one of the UK's largest networks (I work in I.T.) and the Government used to have a bunch of their servers in our server room. Without going into too much information, the Government can basically take what they want. Some actions required a court order, but there was nothing stopping them doing whatever they wanted. SMS logs, call records, your information - you name it, they have access to it.
All SMS's you send are archived and available for perusal by anyone that wants to look. Ever taken an embarrassing photo and sent it via SMS? It's on the server. Ever sent an SMS message in your life? All of them are archived. They are meant to be deleted after 6 years I think, but they are kept.
All this information can be downloaded to a laptop or whatever. Baring in mind that this information can easily be copied to another laptop and then this laptop can easily be stolen... It's so easy for your personal data to end up in the wrong hands and posted all over the internet, sold to another party or used against you.