Zero!
I've always liked the fact that sports provides a platform to imitate life with offering the challenges of perseverance over obstacles, and the ability to fight against all odds.
I come from a background of more "aggressive" sports where trash talk and purposeful distractions are all part of the game (Hoop, Football). I love tennis, but hate the "country club" etiquette that always painted it as a "wimp" sport in the eyes of other athletes.
If a player can't get over some noise and distractions, a player is weak...end of sentence. I regularly play with a good group of 4.0-5.0's in a city park with dogs barking, skaters, helicopters above, sirens, bums, etc, etc....focus and block it out...you can always tell when a country clubber stops by...they leave frustrated and on the tail end of a straight set beat down.
Trust me, me and my buddies respect the "tradition" of etiquette, but some of the most fun matches we play is amongst good friends when "trash talk" is not only allowed, but encouraged.