Is "polyphasic sleep" possible to achieve?

Polyphasic sleep refers to the theory that total sleep time in any given 24 hour period can be effectively reduced to 2–6 hours by sleeping, not in a single chunk, but in many 15–45 minute naps throughout the day as well as (in some variants) a “core sleep” period of three hours or so. Several bloggers have written about their experiences with Polyphasic sleep, but I was wondering whether the collective new anything about the theory?