I suppose it was merely a matter of time before this happened. Google gives away so many services and remains largely quite innovative. That it has become the one dominant x in any number of areas, including search and email, makes it an attractive target.
As Jacqui Cheung explains at Ars, though, at least one of the competitors bringing the complaint may be undermining their own case with their linking and aggregation practices which could be seen as legitimately running afoul of Google’s web spam filters rather than any explicit discrimination.
Google, of course, is trying to reinforce this view, that they aren’t doing anything intentional to suppress competition. The EU has traditionally been harder on questions of monopoly, though, so it should be interesting to see what they find as the investigation continues.