If you're so big, you must be doing something illegal, that seems to be the thinking behind most of the antitrust investigations against Google. Most of the accusations are over things that the other big search engines are also "guilty" of, more so in most cases.
But the European Commission has been known to issue huge fines over this type of things, so Google is playing it safe and is looking to reach a settlement with the EC.
What that settlement entails is anyone's guess at this point. Google, understandably, isn't saying much. But it did send a letter, signed by Executive Chairman Eric Schmidt, to European regulators offering to discuss things.
The EU regulators have several concerns over Google's search business. They believe the company may have abused its position to prop up its own services at the detriment of others.
All of this is based on accusations, coming mostly from struggling competitors, be them unknown copycat product search engines or Microsoft subsidiaries, nothing has been proven. Likely, nothing can be proven. But proving your innocence is becoming increasingly expensive.
Another thing regulators complained about is Google using snippets of data from third-parties, i.e. reviews from other sites on its own product pages, without consent. Google has argued that this is fair use, but has stopped the practice for a couple of years now. The other two main concerns are over its ad business.
Google has maintained its innocence but is probably not looking forward to a lengthy and expensive lawsuit. It may be looking to settle fast, pay a fine and be done with it. It may not be so simple though, it remains to be seen whether it will be forced to do any changes to its search engines.
Having authorities say what a search engine can and cannot provide as answers doesn't sound like a good idea and is probably the beginning of a slippery slope.