From CBS Sports' Clark Judge:
Here's hoping Baltimore's John Harbaugh didn't start a trend when he threw a flag to challenge a sideline reception, then picked it up after talking the play over with officials. You throw the flag, you must challenge. Period. Harbaugh caught a mulligan, and he shouldn't have. When he challenged a catch late in the fourth quarter, Colts' quarterback Peyton Manning spoke to Harbaugh and referee John Parry and later said he told Parry not to talk Harbaugh out of a challenge. We get the message, Peyton, and the NFL should, too.
Here is how you you prevent such things from happening: When a person throws the challenge flag, they must challenge. Even if the play is so obviously not worth review, it gets reviewed. Thus, the team throwing the challenege is charged a timeout. If a team throws a red flag and then changes their mind after talking with the refs, that's a delay of game penalty and an automatic first down for the opponent's offense.
The onus must be on the teams to know the rules and use challenges appropriately.
Seriously, when you throw the red flag, you should NOT get a mulligan. Harbaugh threw his flag because (in theory) he saw his defense was getting no-huddled to death by the Colts offense and wanted to give them a breather without wasting a timeout. The problem is, that's why teams get three timeouts per half. While this is not the out-and-out cheating Mike Singletary and the 49ers did when they supposedly instructed players to fake injuries on the field in order to stop play and not waste timeouts, it is a pretty shady practice by Harbaugh and the Ravens, and the NFL needs to stop it.
Bottom line, if the NFL wants to stop shady tactics like the one Harbaugh seemed to employ Sunday, flag them for delay of game. That, or force them to challenge a play, and thus forfeit one of their timeouts.