Others brought up being stalked, but anyone who's been on the receiving end of that can likely respect having a greater control of what information about themselves, be it real or that of digital avatar, is out there when it comes to offering peace of mind.
Sadly, I lost a friend to the game when she chanced upon meeting the wrong guy. They kind of hit it off at first, but he got clingy. She eventually blew him off, but he'd have nothing of it. Such began a smear campaign of personal harassment from him, his mules (often deleted and recreated), and whatever buddies he could cajole into giving her crap. He had search comments set up, which at the time, I guess wasn't a bannable offense when including a player's name. He'd go to whatever zone she was in as a higher level job and thin out the EXP camps she and her party was participating in (Highest she got was to 58) and occasionally MPKing if it was an option. She'd called the GM on him multiple times. Hell, I even called for her after trying to moderate and him being snappy at me, but all we got was the canned response to just blacklist him. Eventually she just lost the will to log in, and soon after canceled. I tried to get her back after it seemed like he quit, but the damage had been done.
As is, I've received the occasional unsolicited trash talk on my old server simply because I'm one of those kooks who feel RDM + Melee shouldn't be a solo toy. Some might sit here saying they have nothing to hide, people should grow a thicker skin, or whatever, but I see it more as a preventative measure for keeping those with lesser restraint and morals from gaining an avenue to attack people from. I'll never rule out the possibility of accounts themselves being at risk, as such could create a trail of breadcrumbs leading to a blog, linkshell forum, or wherever that someone more tech savvy might be able to extract such info from less secure sources. Could've been a simple old PM to a friend, "Hey, I'm going out of town. Could you log me in for Dynamis if X drops? blahblah" It's happened, and lords no phbb and such has vulnerabilities.
Overall, I'm fine with the mandatory linking of a character for further forum use, but said character's information should have the option of being blocked to all but administrators. And if people can emulate this effect just by picking a mule, there's no point not to.