Twitter has changed it’s blocking policies in a simple way. When you used to block a user, you would block them from getting updates of your tweets. Now when you block them, you effectively just mute them. Many people take issue with this — often blocking stalkers, exs or just assholes who they don’t want seeing their updates to maintain privacy. The problem here is that your tweets are public information and the problem of blocking single users from public information is exceptionally difficult. Ask anyone who has tried to run a forum or an IRC channel and has had to block someone their. Crazy IP wildcard strings to ban ips and all that, only to have that STILL be thwarted. Under the old system, the only thing the blocked party had to do to view your information was to go to your account (which seems to be the thing most harassers do anyways… I mean, do you follow all those political figures you hate and tweet angrily at on occasion?). Even if that policy was changed, all they would have to do is log out, since, by default, all tweets are public. Blocking, as a denial of information to the blocked, was, at best, an inconvenience.
Also anyone who has ran a forum or IRC channel will tell you — the first thing someone who’s banned will do is try and evade their ban in any way possible. The same is true for twitter. This is where sockpuppets and troll accounts pop up like a hydra to endlessly harass you. Now your harasser isn’t just anonymous, they’re super-anonymous. You can’t even tell them apart. Also in my experience, the best way to block someone has always been a silent one. I’ve seen this on forums — you hide the persons posts from everyone but themselves and eventually they just get bored. That occasionally breaks down on forums due to how they work (at least SOMEONE has to respond to me!), but that seems like a policy that would work excellently over a service like twitter. This twitter policy change seems to be one that trades an aspect of blocking that fundamentally didn’t even work to begin with (the denial of information) for more obfuscation. A policy like this will hopefully keep down the creation of new harassment accounts and keep harassers in the dark and the only thing lost being the illusion of security and privacy.
This might not all work out and there might be ways the old policy actually worked that I wasn’t aware of, but I think this is at least a good explanation for the rational behind the change and how it was aimed to help victims of harassment.
What I would like to see would be ‘semi-private’ accounts. Accounts closed to those not logged in and without a twitter account. This at least makes the process of blocking way more definite and effective (.. even if they just have to add a new account to follow you, but other policy options could help, like the requirement for accounts to be over a user defined age or something). This could be less oppressively closed that a ‘private’ account while still providing a lot of the benefits.
edit: That was short lived. Twitter has rolled back the changes. While I preferred the new policy, I don’t feel the rollback puts things in a partially worse state. But I’m going to say this, because a lot of people don’t quite get this. The block system does not stop people from stalking you. It does not stop them from seeing your tweets, and is only a minor inconvenience. It does protect your personal information from getting into the hands of jerks.
So basically be safe.