> If Chrome intentionally started rendering Yahoo slower, that would be blatantly anti-competitive. This is, in effect, just about the same thing, only with practical reasons behind it (much like their were practical reasons behind integrating IE into Windows).

This seems to be a poor analogy.

One of the main draws of capitalism is to encourage companies to compete by offering quality products. One of the main drawbacks is that companies are also able to compete by sabotaging the ability of other companies to offer quality products.

The second is the reason for anti-competitive laws. Sabotaging Yahoo falls into this category. Offering a better product that what's already on the market - especially without impeding the quality of the old product - falls squarely into the first.