Like Mark, I am a lawyer who defends personal injury claims (in my case, largely physican and hospital malpractice claims) and I have done some general liability work of the kind that Mark describes.
These are common claims; plaintiff lawyers may be happy to sue the golfer who hit the errant shot and who perhaps failed to yell fore, if -- IF -- the golfer has personal general liability insurance coverage for that kind of claim. The basic problem for the plaintiff side is that "assumption of risk" is a standard defense. The assumption of risk doctrine indicates that we all assume some risks when we go out on a golf course. Golf happens. If we, and our fellow players, never hit errant shots, it wouldn't be golf. Since we hit errant shots ourselves, we should reasonably assume that others will too. And we might just get clobbered. If you can't accept that risk, don't play golf.
For claimants who can't otherwise find a deep-pocket defendant, or whose cause of action for golfer-originated negligence is barred, the next step is a claim for negligent design and construction of the course. And they are very, very common claims. The cornerstone of those cases is usually the expert-witness opinion testimony of a golf course architect for the plaintiff.
Here in Michigan, there are at least a couple of reported appellate decisions in which Bill Newcombe (who coached the Michigan men's varsity team for a few years, and who designed a handful of mostly unremarkable courses in the Great Lakes area) supplied the testimony for the plaintiff. My guess is that he's done scores of those cases that settled if he is featured in three or four reported cases. The pay is usually very handsome for those experts. Not Nicklaus-Design-fee handsome, but probably $500 per hour handsome. I don't know who else does it around here. Mark may have run into Newcombe.
The logic of these cases is debatable. A site like GCA could find lots to discuss in the detailed merits of some of these cases. (We could find almost anything to debate about golf course architecture, right?) Most of these suits, like most personal injury cases that I work on, are substantively garbage. Meritless. Mark and I might be able to debate tort reform in another thread, but while there are lots of federal (i.e., FRCP 11) and state court rules (i.e., MCR 2.114) against frivolous pleadings, those rules are almost never enforced. Michigan has some fairly advanced tort reform that has survived challenges in the state supreme court, as well as a court rule that can shift the burden of trial costs and attorney fees, even without a "frivolous" finding. But that's probably too much legal minutiae for GCA. I sure hope so.
Mark, when I lived in Chicago I played and practiced regularly at Oak Brook, in order to use their CDGA handicap terminal, before they offered online entry. And, as you know, it is a fine public facility with excellent practice facilities. Private club-quality for the most part. It is the public track that was part of a large land donation by old man Butler and it abuts Butler National GC; they used some of the holes at Oak Brook the year that Butler flooded when D.A. Weibring won the Western Open. (And, I'll be happy to give you an affidavit to the effect that while it may be possible to hit someone with a golf ball at Oak Brook, there was no negligent design...
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