As an investor in this company, I expect employees to do the job they were hired to do, not playing on the internet and posting negative comments. This is a concern especially during work hours!
Your superiors expect you to do your job and bring value to this company. A number of companies are now banning the personal use of cell phones while they are working. This helps to eliminate employees wasting the companies time and money that they have invested in them. The receptionist can field any emergency calls.