I don't see that it's all that much of a problem if you use common sense. LiveJournal's been around since around the time I first started really dating, so almost all of my relationships have been in the digital age.
I've been both followed and done some following of my own on social networks with exes. The extent of my following was stumbling on my ex's DeadJournal when she left it in the internet history on my computer, and that wasn't even an after the fact thing, we were still seeing each other, so I checked it out and found out it was actually a backup to her LJ that she'd made to hide shit from me (Including the fact she was contemplating cheating on me), so I broke up with her the evening I found it. Said girl called me a scumbag for looking at her "private stuff" (Which she'd posted on a public forum, without any kind of lock on it and then checked on MY computer), but I still don't see that I did anything wrong to this day. I originally assumed she probably intended for me to see it so that she could get out of the relationship without having to dump me, but apparently she took the breakup horribly at first and I was just giving her intelligence too much credit.
Said girl subsequently LJ/AIM stalked me for a while and a later girlfriend did the same with a couple friends of hers, but that's the worst I've ever gotten. Since then, I've kept my MySpace and Facebook private and have yet to have a problem result from it. I always remove a woman when I stop seeing her just so I don't have to follow her life. It's not a problem if you don't want it to be, nor is it anything particularly new. We have these things in real life called social networks as well. We have our co-workers, our friends, our family, our friends of friends and we'll deal with these awkward questions and tensions between friends of friends and the occasional unwanted update on their life with or without stuff like Facebook.
This only becomes a problem when both parties refuse to let go, and that's a personal problem and not a new one at that. I've caught more exes spying on me outside work when I did retail or making unwanted calls to my cell phone than I ever dealt with spying on me through social networking sites. Maybe I've missed some instances, but that's not my problem, as I don't follow their lives. It's not hard to remove them and put them on ignore lists if they don't get the hint.
I think the real problem is that people just put too much emphasis on Facebook politics in general. A friend of mine was complaining to me about how his ex is on his ass for deleting all his old pictures of her from his Facebook and he apparently saw it coming. I seem to be in the minority in terms of being willing to decline friends or remove people because I know it's for the best.