Not that this technique can't be done successfully- but see it as a source of problems for the average homebrewer.
I see fermentation issues stemming from low cell counts or low viability as the main source of problems for homebrewers at every level.
Making a starter for EVERY batch is difficult to accomplish, even if you're really dedicated. With good sanitation and storing practices, harvesting and repitching yeast can significantly increase the quality of your beer.
The keys are sanitation, storage, and repitching the correct amounts. Dumping fresh wort on an entire yeast cake creates almost (just?) as many problems as under-pitching.