Ironically, I think you CAN be discerning if you use the default. In the case of cell phones, most people change their ring immediatly. In order to be unique, I've left mine with the default Nokia ring.
This is my point.
Said crass consumers feel the need to "express themselves" through the procurement of ringtones embodying elements and figures from today's popular culture.
By keeping the default (or something utilitarian and does the job, i.e. a simple ringing and/or vibrate as your needs entail) you're having a kind of passive-aggressive protest against the capitalist establishment where products are advertised to you everywhere.
You're saying "no!", you won't allow your phone to be used as a marketing tool for celebrities or other consumer products.