The Internet's content can be split into many pieces, but it can be characterised into just 2 (well 3 if you count all the porn!): what people know and what people think.
What people know is simple; it includes all the journals, academic papers, research, medical journals, technical specifications and documentation. All of these sources are considered true (at the time of writing). What people think is also simple. These are (but not limited to) blogs, forums, comments sections, Facebook and Twitter.
But wait... is it really that simple? No. If you know my mate Switfy, he talks like it's true but he has no idea and is generally just making it up. So at the end of one of his explanations we have to ask: "Is that true or Swifty-True?". The Internet is still run by people and everybody lies. In some cases they may not know they are telling untruths they could just be mistaken.
There are many places devoted to collecting peoples opinion. Sites like YouGov ask people how they are feeling about their lives, their aspirations and how they feel about the current state of the country. It also conducts market research.
There are several examples of mistaken truths in action. The UK press reported recently a story about Nadine Dorries M.P. and her blog. She had been keeping a diary reassuring constituents about how hard she was working but caused outrage when it was discovered that about 70% of it was untrue. Another ongoing example is that of Wikipedia. It's content is generated by people, most of the pages are written by the experts in that field, but a lot of them are not. Wikipedia has started requiring citations to back up each statement made. This reduces the number of vague or inaccurate claims but they can still be indexed, searched and referenced.
Every couple of months I get a scaremongering chain email from one of my friends who seems not to be able to tell the difference between a genuine email and a hoax or spam email. They tend to read the subject of "Let stop baby rabbits being used in underwater mining" think this is terrible and send it to everyone they know. Most of them believe that because they "think" they know who sent the message they automatically trust the contents of the email. Some are not so obvious, for example the Marks & Spencer Voucher Giveaway Hoax is one such email I tend to get a lot around Christmas time. It shows that in some cases the original recipient has not even read the email before passing it along. If you read the email it says that someone will give you £100 for passing the email to 8 friends. In fact they are doing the spammer's job for them.
Spammers are lazy. They just cut and paste the email which makes it really easy to lookup at Google. Copy one sentence from the middle of the email and paste it into Google. You will always come up with a hit because you are highly unlikely to be the first person who is targeted and most of the circulars are reused from a couple of years ago.
You, as an Internet user, must decide for yourself what is true and what is false. Often there is just opinion which is very subjective and dressed up as truth. Often there is someone trying to con you. In fact, it's just like life.