A very pronounced undulation is another way an unscrupulous dealer could possibly get you to remove a perfectly fine tire from service......but I have never seen/heard of anyone doing it.............because most likely the replacement tire is going to have the same characteristic.
I have to explain undulations several times a week (even this morning) to concerned customers, who don't see the difference between an indentation and a bulge.
I always explain that with undulation, the same indentation will be in the same place on both sides of the tire........whereas a bulge (broke cord) will only be on one sidewall. You can just reach across the tire and feel it with your fingers.
I can find undulation on just about every tire....sometimes as many as in 6 different places. Here is a pdf link explaining undulation, so you can better arm yourself with knowledge........especially if you are in Nevada.
http://www.coopertire.com/html/pdf/S...Bulletin54.pdf