A recent case where an HR manager who posted his CV on the LinkedIn.com web site highlights the dangers of revealing too much personal information n the Internet. He contends that he was forced out of his job as a consequence. While there is no law saying that you must not provide your CV to other potential employers it does demonstrate a certain lack of commitment to your current empoyer. It will be interesting to to see the outcome of the industrial tribunal.
Any employee tempted to use their employer's computing facilities for personal internet activity should have a look at the capability of spyware tools available to employers should they choose to investigate the activities of their employees. Strictly speaking employers in the UK are not allowed to use such tools unless they've previously warned the employees, but it is something easily handled by fineprint on the employment contract.