What happened to you is harsh but in my opinion there is an important distinction. Chatting with colleagues is building relationships that help get work done in the long run. Chatting on here is just abusing your employer's trust and wasting their money.
Got to agree with you , people who are bleating that its notfair they are not allowed to use company facilities to post on here etc should think themselves lucky.
where i work the number of people with access to a computer is limited to those who need to use one as part of their job role and even then they only tend to have access to the intranet rather than the internet based on job role need.
each job element has been timed to work out how long it takes to make any particular sub assembly based on sales forecast and man power so they know how many people they will need to build and that forecast speed.This means you do not get time to misuse company time or facilities and the only time you get to socialise is during planned breaks where you are allowed to use mobile phones but you are not generally allowed to take personal calls during production time unless your expecting something important for all of the above reasons meaning that if you spend time doing this you will stop the factory and everything is based on just in time within a limited buffer.
If a supplier is late delivering parts they can be responsible for the cost of loss of production, which is thousands of pounds a minute for a full line stop.