Assuming they did prime place their own products, this is not a recognized antitrust harm (it is not bundling or tying, despite random claims on HN).
Do you think it's ethical or good for society simply because it hasn't yet been ruled illegal?
My opinion on things related to competition/antitrust are based mainly on evolution of law and economic viewpoints.
Basically, over the past hundred years, courts have moved away from (and economists have strongly supported) declaring these kinds of things as "per-se" illegal precisely because evidence has not shown that you can simply point at them and say "yeah, this hurts competition" or "yeah, this hurts consumers", despite what one may think.
In some cases, this evolution of law/economy has pretty clearly turned out bad for consumers price-wise (with the return of folks requiring retailers to sell at certain minimum prices).
In some cases it hasn't.
This particular thing, hard to say.
The second part of your comment only mentioned prices as a factor in terms of what is good or bad for 'consumers'. I realize that you leave room for other ideas of what is good or bad, but in lieu of mentioning anything else, it seems as though this is all you are willing to put forward as a criterion.
I guess I understand a little more about your perspective, but not much.
Truthfully, this kind of stuff is only tangentially interesting to me: Companies without physical resource monopolies (ie oil, diamonds, whatever) tend to come and go despite all efforts to the contrary. I don't expect Google, Facebook, or anyone else will be any different.
Harmful indeed.
90% market share + hiding competitor sites to eg Google Places is punishable by EXISTING EU law.