You can find a recent United State District Court survey regarding Rule 11 on the web now, go here for the information.
Do judges think that groundless litigation is a big problem?
Nearly 85% of the district judges consider groundless litigation [in cases where the plaintiff is represented by counsel] as no more than a small problem. Another 12% see such litigation as a moderate problem.
Only 3% of the bench views groundless litigation brought by plaintiffs who are represented by counsel as a large or very large problem.