While I have to agree that it would be nicer to have the use of colons in titles, I don't think it would be better to have "content:" preceding every Wikipedia title. Colonless page titles could be automatically converted to content: titles (so that [[foo]] would be saved automatically as [[content:foo]]), but it would make the system more complicated and more importantly it would make the titles and the URLs uglier.
This is really more of a technical issue than a policy one. I mean, from a policy standpoint, it's great to have the use of colons in titles. If there aren't any technical objections, we should do it. But, of course, there might be technical objections. (Cc'ing wikitech-l.)
Larry
Thus instead of the ":" being a reserved character anywhere in a title, only "user:", "talk:", "wikipedia:" etc. need to be reserved. Any other uses of colons should be fine. This will let us have entries for books with standard formatting of the subtitle (e.g., "The Muggles: A Tale of Woe") or other natural uses of the colon.
There is a simpeler solution. The actual contents of Wikipedia get the namespace "content:". If everything is prefixed with a namespace then the first colon is always the end of the namespace.
That's perfect.