When you consider the extent to which rules officials go to see that there is absolute compliance in virtually all other areas, the inability to enforce pace of play rules is startling.
The rules of golf are written with enough specificity in most cases that it becomes a matter of establishing the facts and applying the proper rule. With respect to the pace of play, any number of factors can cause a player and the field to slow down. Weather and course conditions are often to blame. Lost balls and difficult setups in the first few holes can back up play for an entire day. Also, a much too common tendency in tournament play to call over an official for even the simplest rules issue bogs things down.
Having said this, I have noticed a reticence in qualifiers and local tournaments to apply stroke penalties even when the player is clearly liable. Conflict avoidance is probably the reason, and often the guilty players aren't in the mix.
I see my role as a very junior official to facilitate play, so even though some OICs (official in charge) don't like that we interact with players on pace of play issues- and some players don't like to be told that they're behind- I generally find a spot after they've finished a hole to provide guidance. I appreciate when players ask me how are they doing on time as it tells me that the starters have done a good job of stressing the pace of play policy.
The unfortunate thing is that most golfers do not believe that they are slow. And unlike Barney who lets faster players through, it is not a common practice at many clubs, specially if the faster players are walkers.
The best way IMO to overcome slow play is from the top- the tournament committee; the head professional and applicable committee at the club level. At a private club, the tee times might be tiered with the first hour or so reserved for fast players and the afternoon for families, Barney and his ilk. Thoughtful course set up helps as does peer pressure.
Setting reasonable expectations for the type of play of the day is important. IMO, OICs are much too liberal (4:45 for a threesome in qualifiers is not unusual). But while building ample time might minimize pace of play issues, it pretty much ensures that all but the first few groups off will take that long (the task expands to the time allotted- Mgmt 101).
Mike Cirba- I think that distance off the tee has little to do with the problem. Pre-shot routines, strategizing with a caddie or yardage book, and deliberations on and around the greens seem to me to be the bigger issues. I worked a USGA Women's Amateur qualifier a couple years back where many of the players (many on college teams) could not pull the trigger without the direction, approval, and alignment by their caddies, even on a 2' putt.