If you kill PTCUser.org without providing an adequate alternative (read "email notification for ALL posts") then you deserve what you will get - more bitter cynical users that question your every move and refuse to trust the most transparent motives.
Sound familiar? It's the very thing you've been trying to patch over ever since the heyday of the 80's and 90's when you built a solid reputation for screwing your own customers. Good times...
Never mind you're giving Solidworks another example of why they are the easier company to work with - customer focus is just another fad, like pet rocks and MySpace. The really cool companies are establishing a single source of information. Align your strategies, control the message, feed the pipeline... and pretend you don't see that simple solution over in the corner.
Seriously - where else are you going to find knowledgeable global experts willing to share their in-depth understanding of your products... FOR FREE!! No company can afford to offer that kind of support. And trust me - these people do not have the time to visit your shiny new website multiple times a day to see if anything worthwhile appears. Not gonna happen.
Of course, this assumes you're not simply attempting to drive more customers into overpriced maintenance plans by cutting off alternatives. Because if that's the case, you can bet Solidworks will be spiffing up the welcome sign for more ex-PTC customers that bolt at the first chance they get. I won't mention names, but a company I'm familiar with dumped half their seats of ProE and started a whole new department using Solidworks. Because cost.
CAD Systems Administrator
Varian Medical Systems
Palo Alto, CA USA