Also, there were issues with users using their own PC's as they were not maintained by the company I.T. Dept. You also have to worry about licensed software. Is the software on the PC fully licensed? Are they using Home versions of software (Office perhaps), or other software that can't be used commercially. If the user is doing work for you at home on unlicensed software, will your company be put at risk?
You can control things like this on company PCs and Laptops, but you can't control them on home PCs.