Technically, it is a logical strategy. Ethically, it's shady and you will undoubtedly take heat for it.
If this is a league with good friends, I wouldn't recommend it because you will at some point have to talk to these people again. If it's a league with people you probably will never interact with again, it isn't as big a deal.
Above all, if this is a year-to-year league and you're still considering it (even though I don't recommend tanking in a year-to-year league), TALK TO THE COMMISH! Make sure you know how he will react to you doing this. If he will kick you out of the league, then obviously don't do it.
Personally, I don't think it's worth it either way. What happens if the Steelers pick off Brady three times (I can dream, can't I?) and his team has an awful week, whereas the team that you let into the playoffs explodes and beats you by 30+? There's no way to predict how a team will do week to week.
Kudos to Leber
for the amazing sig and to Metroid
for the userbar and making them both fit
2008 and 2009 Defunct Dynasty League Champion