At first when I read this, I thought, "How could the EU possibly come to this conclusion? Firefox has over 20% market share and is still climbing. Are they dumb?" But then I sat down and thought about it.
Who prompted this investigation? Opera. Opera has not had the success that Firefox has enjoyed. Now, most of use don't see this as a problem, but to the EU, it is a problem because Opera is a European company. The way the EU sees this, it's not a question of alternative browsers being able to take root, (Firefox already shows that is possible) it is a question of alternative EUROPEAN browsers being able to take root which has not happened.
Think about the consequences of this decision. Considering that Mozilla has already stated that they would not bundle their browser with Windows, what other "major" browsers are really left? Just Chrome, Safari, and Opera, and I have trouble seeing Apple and Google forcing themselves upon MS. Really, Opera is the only browser that would really benefit from this.
The way I see it, it's all politics, they want to help Opera, the poor European browser, fend off those terrible Americans who can build better products.