Between captcha and activation emails there has to be some human interaction. Since I'm not an admin I cant change the forum settings so any enforcement is best applied across the board. I catch the majority of spammers during the new member moderation period or when they register their account.
I'm not saying that onelove is a spammer, but if I allow one member to link ABC then others will also want to link XYZ. Then I'll have to deal with "but you let LMNOP link ABC, why can't I link what I get paid to spam? That's not fair!"
We used to allow linking and that got abused so I changed it to "no links to sites that sell anything grow related" and that didn't stop them either. Seriously, if I had better tools to deal with the spammers I'd allow linking but it's easier to stop it all, for now, than to police each link.
As I've said, nickgreen can override my decisions if he wants, I wouldn't take it personally if somebody complains and he tells me to do something differently. It's just what I've been doing to stop spammers and make the forums a little nicer for everyone. Unless you want to see spam ads for baby car seats and viagra?