Cool I can now use this in my closed source project without ever giving any change back!
Hate this GPL that requires you to give back anything if you let others get your product.
Rails is MIT licensed and as a result we have seen a lot of companies build their web applications on Rails and build very successful businesses, but we have also seen a range of opens source plugins/gems and applications themselves built around Rails which have resulted in a better web community.
This is 2012, developers who care about something like Meteor also care enough about open source to give back. We don't want developers to be forced to make their products open source, they should feel compelled by the enjoy of helping others.
In fact, I expect more community contributions to come in. MIT means (perhaps) a lower percentage of users will give back, but there will be a higher absolute number of users since the license is more permissive.
Permissive licenses are just fine (arguably, better).