Why have forum rules? Why enforce the rules?

[writespeak]

Of course there are reasons, and I know what I think. I'd like to know how other people answer the subject line questions. :)

Why do we (at whatever forums we represent) have forum rules?

Why enforce the rules? What are the goals behind rules enforcement?

Thanks!

Lois

[BurakUeda]

What level of "forum rules" are we talking about? The whole forum concept? like:

No need to register
No moderation
No limits to posting pictures/uploading files
No restrictions to admin area
etc.

Or the rules /after/ the registration?
I am guessing it is latter so; we have rules to attract more visitors, by providing a controlled discussion arena and -limited but effective- protection from spammers/flamethrowers/trolls.