Understand about his workload, but the poster who points out that he ends up stepping on aircraft is correct. When you hear those "beep" and warbling sounds, that's two radio signals mixing in the monitor receiver (not an artifact of the editing down of the clip.) He seems to be anticipating the end of an aircraft's transmission, and then jumping on his PTT button when he expects someone to be done talking, instead of waiting to actually hear the end of the transmission. I understand the concept of a "blocked" transmission. The guy in WHP tower has been controlling for years and was a pilot for many years before that; in other words, don't think for one second that he's losing control. As I mentioned, it is hectic airspace. As far as the blocks go, at the time, he was working tower/ground combined and dealing with several aircraft all at once. Many of those blocks aren't anticipation, they are two pilots trying to call up at the same time.
Again, I understand it's busy, but that's a bad radio habit, and I think it added to everyone's stress on this frequency (including, unfortunately, the controller's.)
Radio etiquette goes both ways as well. There's nothing worse than trying to call up a tower or a TRACON but being unable to do so because a pilot is being long-winded. At Whiteman, there are a serious number of weekend fliers and student pilots who just aren't that great at Keeping It Simple, Stupid. There are helicopters everywhere, 10-15 aircraft in the pattern or trying to land, several trying to depart, and in this audio clip, the restrictions in place because of 737 departures out of Burbank and the normal craziness of VNY. In that situation you should be flying your airplane, not telling the controller how nice the weather is outside.
All your points are valid, but none of them validate or justify the bad habit of stepping on the end of somebody's transmission. It's a fundamental procedural requirement of a half-duplex, two-way radio link that you must wait for the incoming transmission on the frequency to drop before you press your PTT switch; if you don't follow that requirement, you have NO WAY of knowing how much of the incoming transmission is continuing underneath your own carrier. This isn't specific to ATC, it's true of any half-duplex radio link.
We use tools (like radio communication) to manage risk, and we pilots and controllers follow the procedures attached to those tools as closely as possible because that minimizes risk. Just because a bad habit "works out OK" 95 or 99% of the time, or because workload is heavy, or because one is distracted by running multiple frequencies, does not insulate you from the risks or consequences of that bad habit.
Bottom line: it's an unfavorable risk/reward tradeoff: if he guesses the end of a transmission right, he doesn't really increase the efficiency on the frequency that much by getting a half-second jump on his own transmission (low reward), and if he guesses wrong, and the transmitting aircraft adds something significant at the end which gets covered up and thus not received by the controller, then as I pointed out earlier, it has at least
the consequence of increasing the tension on frequency, which is already in plentiful supply in this clip.
Finally, regarding the implication that this bad habit is driven by workload of the moment, take a listen at 1:02 into the clip in the "airplanes everywhere" thread: http://www.liveatc.net/forums/atcaviation-audio-clips/kwhp-'airplanes-everywhere'/
. Clearly that was not a high-workload situation.