These are my opinions—-I would welcome more discussion from everyone here.
1. There's a difference between committee membership and membership of this wikidot site. Site membership I think is important because if anyone from anywhere on the internet can post, then the site's quality can go down quickly. I used to run a wiki that was freely editable, and it was overrun with spam posted by advertisers. True, we could edit that stuff out and think about banning certain IPs, but I'd like to avoid a time-consuming cat-and-mouse game. I don't think requesting membership and requiring a valid email address is unreasonable.
2. I get your point, and I think it depends on your view of the situation and basic challenges actuaries face. If there is a dearth of information, then we would want as much posting as possible, to avoid blocking information. On the other hand, if actuaries are extremely busy and overwhelmed with information, then narrowing down the content may be more useful. I think actuaries are usually in more of the latter situation (for instance I see there are 5 new articles on r-bloggers.com this morning—-meanwhile I'm lucky to get through Variance). But I'd like to hear others' options.
2b. To expand on the above point, there are plenty of avenues for free speech on the internet, and anyone who wants to post something to their personal blog can. Several committee members already do this. And there are already sites like r-bloggers that will publicize blogs on different topics. What can the committee add to this? On the other hand, as far as I know, there's no site where an actuary can go to get hands-on explanations, code included, where they know their time will be rewarded with techniques reviewed by their peers and already proven to be useful in solving real problems their peers have faced.
3. Well we already have this whole special site opensourcesoftware.casact.org :) We can make pages on it as we wish.