... is created by volunteers in their spare time (there are exceptions,
and some people get caught "doing it" at the workplace; however, we're
talking about the mainstream trend);
... offers full, free access to all of the information it stores to its
respective users, who can use it in any way they like, and even alter it
in any way they want (there usually are some peer-imposed limits, but
again, we're talking about the concept);
... has even its internal workings free to study, fix and enhance by
anybody who has the interest and time to;
... is able to store virtually unlimited amounts of data;
... is enhanced and refined each day in any direction;
... is inherently plagued by disputes and even wars -- and it can only
survive if it is able to negotiate these conflicts; however, each such
conflict makes it stronger and more able to negotiate such internal
conflicts in the future (unless it kills it, of course);
... stores accurate facts and erroneous opinions, useful insight and
useless trivia, exhaustive information in certain areas and sketchy data
about other domains -- however, the overall trend is towards fixing the
wrong data and filling in the missing information;
... needs minimal maintenance compared to its resources;
... has been able to maintain an active interest, and even fascination
for some, for a very long time;
... has intrinsic human and social value, since it stores information
collected by the mankind;
... is most probably the most wonderful, fascinating and open-ended
mechanism you'll ever see in this lifetime:
It's the human body.
(April Fool's :-))