Below is a chart of the percentage of distinct 10-Q filers who have expressed "substantial doubt" in their filing. Time period is the second quarter of each year (not much will happen 10-Q-wise in the next couple weeks).
Although substantial doubt could occur anywhere in the filing (because my program searches the entire document) the samples I've eyeballed show it in the Going Concern section of the Basis of Presentation Note (this will get easier as XBRL rolls out). Anyway, it's not what most companies want to say anywhere in a report.
As you can see the percentage is rising. The number of firms expressing substantial doubt is growing even as the number of filers is declining. Looking closely at the 2006 group about half did not file a Q so far this year.
With no IPO market it looks like the public regulated capital markets will continue to shrink. What that means, if anything, I'll leave to better minds.