The quickest way to ruin the potential for an inclusive, intelligent online community is to have a poor moderation system (or none at all). Many people fear the accusation of 'censoring' others, or violating their free speech, even though those constitutional rights do not apply to private citizens' control over their own property (i.e. blogs, websites or forums).
The example of the Kathy Sierra debacle and it's resulting debates on web conduct, as well as a more recent event on Wired, illustrates clearly why allowing asshats unrestricted access to a web space quickly spirals the entire atmosphere of the community down the toilet. It eventually becomes simply an echo chamber for the lowest of the low, repelling and silencing anyone whom the trolls do not wish to be heard. Any chance for intelligent, constructive interaction in that space is then destroyed.
The actual side affect of proper moderation of a web community is that a free exchange of ideas becomes truly possible once those who are incapable/unwilling to behave like civilized beings are not allowed to usurp control and set the tone to their own low standards. Your personal web space is your own; do not be afraid to stand up for it.
'If Your Website's Full of Assholes, It's Your Fault'
'How to Keep Hostile Jerks From Taking Over Your Online Community'