In the state that it's in today, the Internet can probably be called the greatest achievement of mankind, without the fear of trivializing the concept.
Never before have people amassed such an utterly impressive database of useful and useless information. Then again, I might have to rephrase that last sentence about information being useless. I'm not even sure there is such thing as "useless information".
After all, what's junk for one person, can be true gold for another.
Locating the information that one is truly interested in, can really become a "needle in the haystack" task though, given the vastness of cyberspace.
That is the primary reason online communities came to be in the first-place.
It's always easier to find a useful bit of information where people with similar interests congregate. Not only do online communities make the finding of specific information easier, they can contribute to the creation of new bits of knowledge.