I dumped parts of 3 batches in the past 6 weeks. A 3 gallon batch of barleywine that was over a year old and infected, a dopplebock I tried the ferment warm trick on ythat was horribly estery, and a wee heavy that I didn't oxygenate enough and got a stressed fermentation. Oddly enough these were the first beers I'd dumped in years and years and happened here close together.
Dumping beer while never a good thing is a matter of life, even professional brewers are doing it. If you're not dumping now and again you probably aren't trying new things very often or don't brew enough.