Have shared accounts many times in past with no issues
Here's where it becomes trouble:
Say you Turbo are the person who creates the account and you live in Cincinnati, Ohio. Therefore you will be blacked out of your regional games (Reds/Cleveland/etc) whomever they are, because on your billing info the zip code you entered is considered your "home". Now let's say Hawk lives in Charlotte, NC and will be blacked out of Braves games. Where the problem comes into to play is when you and Hawk log into the account and he wants to watch a Reds game (which you the cardholder are blacked out of) and he can't. So multiply this times 3-5 people and you could possibly be blacked out of multiple cities. Now, if all parties involved are around the same area and will be blacked out of the same games then it wouldn't be a problem.
Only reason I know this is because I've had a subscription to MLBtv.com for 7 years now and gave a good friend my login info for him to use. I'm from South Carolina and should only be blacked out of Braves games but when he logged in from Virigina, I was then blacked out of Reds, O's, Nationals, and Braves. For 3 straight years, at the beginning of each season on opening day I spent 1-2 hours on the phone with MLBtv trying to figure out why I was blacked out of these games and they would have to go thru the process of reseting my account and location. I really enjoying watching the multi view screen where you can watch 4 games at once, and usually have the Mets/Gnats/Phillies/Marlins on along with teams who's announcers I enjoy, Dodgers were one with Vin (going to miss that voice), Dbacks with Steve Berthiaume, Brewers with Bill Schroeder and Brian Anderson, Giants with Duane Kuiper and Mike Krukow, .etc so this is how I found out I was blacked on of those games. Sucks because even though they may have been playing on the road it didn't matter.
Not trying to say it won't work but just be prepared that you'll encounter more blackouts from whichever city the participants are currently in.