Agreed. I'm a little surprised (though not much) to see lock-in so openly touted as a goal. In the long run such lock-in is inherently anti-consumer and a problem many are trying to solve. Look at Facebook these days, which everyone complains about but still uses. What can you do? Everyone's on it. You have no choice. And here we have an article about how to create millions more locked-in, disempowered users.
Now to be honest, the Mailchimp example in the article sounds fairly innocuous compared to Facebook. They're just able to give you extra data and better stats (from what it sounds like; only skimmed) compared to an upstart service. It's a less extreme example because the value-add from network effects is a smaller proportion of the overall product.
But the principle is the same, and this is yet another reminder that Silicon Valley capitalism is as amoral as any other kind. I look forward to someone disrupting the paradigm of non-interoperable web services that let businesses lock people in like this. I don't know if that kind of disruption will have a business plan behind it; I suspect it may not be VC-funded.