I think it is a bad move from Sony. For the casual gamer it seems like an unjustified cost. Back in 2002 I think Xbox Live was great and the Quality of Service for online multiplayer was beyond anything you could find, so back then I though $50 a year was a good deal for a service you couldn't find anywhere, it wasn't a commodity. Online gaming in consoles was virtually nonexistent back then and talking while you played was a novelty.
But now, a lot of people have broadband with more than enough bandwidth to even support video calls while you play, online play is a commodity, any decent game supports it and I think when I pay $60 for a game that has an online component in it, I assume it is coming as part of the cost of the game. I mean, PC games support online gaming very well and you don't need to pay a subscription to use it, that's why I just don't see the added value in 2013.
If they want to charge extra for saving your games in the cloud, for playing your games on any console, for getting some extra games a month, for video chat while you play, for sharing the game footage while you play, for automatically finding the best match while you do other stuff, I'm fine with it, I would even pay for it, but I don't think charging for online multiplayer is worth it anymore.
Also, for online multiplayer, you want to encourage people to try it, specially casual gamers, putting a subscription cost to it, just makes it more hardcore. I don't know if anyone has noticed that Xbox Live community is more hardcore than the PSN community and I personally enjoy more playing with less hardcore gamers.
For casual gamers it is difficult enough to find friends that own the same games you do to play online, now that a subscription is added it will just make it impossible for casual gamers to play online.
Also, I think if Sony made this mistake, Microsoft should start playing Sony's game and making online play available on Xbox Live Silver, that's the type of response I'm expecting from Microsoft instead of just copying what Sony says.
Since Sony announced it would charge for online play, I just won't buy the Xbox One because of the extra $100 USD I have to pay for a Kinect I don't need or want.