Update: Penny Low "apologized": "I was so caught up in the wonderful NDP 2011 and felt so proud of being a Singaporean, that I wanted to capture that moment of pride, at the very tail end of the anthem, to share on FB with my residents. If in my enthusiasm I offended anyone, please accept my apologies. NDP is a time to unite not divide. Majulah Singapura."
Frankly, I don't know how pointing out her faux pas was dividing the country.
Pro tip: During the singing of the National Anthem at the National Day Parade, try not to fiddle with your mobile phone. You are on live HD TV.