New Delhi, Jan. 8 -- "A castle can't fight a war on its own," Jaime Lannister, one of the lead characters in TV series Game of Thrones (GoT), remarked after the northern stronghold of Winterfell repeatedly fell to invading forces. Its real strength lies not in the walls but in the people who guard them and the moat that protects them.

In investing, a moat, as popularized by Warren Buffett, is a business's sustainable competitive advantage, shielding it from rivals just as moats protect castles.

I have argued in the past that steep valuations in consumer businesses are defensible given deep moats built on brand (mindshare), distribution (share of shelf), and product (habit share). But, are these moats beginning to show cracks in today's ...