A question about balancing invested assets

[Rubeskies]

Not sure if you guys have heard of this but I was intrigued about an article I saw that offered the following strategy.


Step 1: Invest $100 a month amongst Vanguard and the 4 major iShares.
Step 2: Choose a target percentage for each one. They suggest 33% in the Vanguard, 25% in the EFA, and fill out the rest with AGG, IYR, and IYM.
Step 3: When you add new money, you add this money to the ETF's that have underperformed or lost money until your percentages are back into their correct ratio.

The idea here is that the ETFs that have underperformed will even out in the long run therefore you are buying low.


What do you guys think of the rebalancing and the overall strategy?