Questions are the lifeblood of any Stack Exchange site. But asking good questions can be difficult, for some people entirely too difficult to bother with. When the Trilogy sites reached traffic levels that made manual review and filtering of questions burdensome for the good folks answering them, we began building systems to detect and slow down the folks who weren't putting any effort into learning and improving over time:

We believe asking questions on our site is a privilege, not a right. If, after a few fair attempts, you haven’t been able to prove that your contributions to Stack Overflow make it at least … not-worse … then we reserve the right to refuse your questions. If we don’t do our part to cull the bad questions, then we risk alienating the true experts who provide what really matters: the answers!

Ask Ubuntu has reached traffic levels where this sort of rate-limiting and outright blocking of questions makes sense, so we've enabled quality blocks here as well. These blocks are based on the community's collective rating of posts from both a user's account and other accounts on the same IP address, thus limiting the ability of folks to abuse the community by just creating new accounts. Blocked users are directed to this page, which explains what that person must do to lift the block. Moderators have access to information on whether or not a given user would be blocked, as well as whether or not they've previously encountered the block, for those cases where it is desirable to provide one-on-one support.

###What you can do to help

Quality blocks are based on the community's rating of questions and answers, therefore the most useful things you can do are:

• if you see a great, thoughtfully asked, well researched question, vote it up — please! Great questions are an art!
• if you see an egregiously sloppy, no-effort-expended question that you feel was asked in bad faith … vote it down.
• anything in between that’s salvageable, edit it!

Don't worry about the exact details of the algorithm used for blocking - in general, it's fairly conservative as far as who or what gets blocked. As always, vote your conscience and encourage new members to participate constructively.