That being said I thought about building a site to compete, but stackoverflow basically owns the market. I have no way of collecting users like they do.
The Internet is not going to run out of space. Just as with Wikipedia, "deletionism" is inevitably an attempt to fix some other problem that could better be addressed some other way. If there's a problem with duplication of questions, that's because the UI doesn't do enough to make the older questions easier to find. (Hint: let users vote on tags, and give karma to users who surf through the suite adding good tags to existing questions.)
Marginally-offtopic questions are especially harmless; if there's a problem with those, let the users police the site by downvoting. If that isn't enough, again, it's indicative of some other problem, such as the lack of some sort of gateway between different Stack Exchange sites.
Ultimately, the mere fact that a site like stackoverflow needs third-party moderation means there is room for improvement at the design level. It may seem that stackoverflow is the craigslist of Q&A sites, but I don't think so. It will be easier to dislodge than Facebook, I think.
Chatty, open-ended questions diminish the usefulness of our site and push other questions off the front page.
I see you have the same bad habit I do, which is to hit 'Reply' and start typing after having read the first third of a comment.
You cannot delete your account on stackoverflow without writing to the administrators via email. It is a manual process for them,and they don't delete your account they just rename it and prevent you from logging in. The questions do persist. I'm pretty sure they also deleted my "spam" questions when they banned me.
edit: the stack overflow account is the only one they deleted/renamed.
Here are my related accounts:
http://superuser.com/users/28269/russellballestrini
http://serverfault.com/users/27551/russellballestrini
I was active, honest, helpful and used my real name.
on stackoverflow my username was renamed to user221014
or
If you want to try again, stick around for some time. Add justifications / context to your answers. Some of your answers were of good quality and got appreciated. I wouldn't stop because some posts got closed. It is a community site after all and the big idea is that others can rewrite most of your post and if it gets improved that way, it's better if it stays around forever.