Definitely agree with SS and Mr. Mxyzptik. You should tuck in your shirt to follow proper etiquette, but it really isn't a huge deal if you're taking wickets and your coach, teammates and officials aren't too fussed about your shirt. Unless you're required to do it, it's just a formality and I'd rather have our bowlers take wickets than tuck their shirts in. Cricketers with shirts tucked in do look better in general but cricketers who take wickets look much, much better. Haha, stupid argument.
By the way, you guys (Dravid and Turbinator) have been required to tuck 'em in by your coaches in "high-level" sports because you play in youth teams where they not only try to teach the sport but also discipline. In fact, discipline is a huge thing for youth sports coaches. If you watch the NBA, there are several players who go for extended periods with the shirts out. If they put them back in, it's because of anal referees and that's the only reason you should have to tuck them back in: anal referees or an offended coach or teammates. AFAIK, neither Chappell, Dravid nor ICC officials care about this so Munaf doesn't need to worry about it either.