Disagree with the original post... I think they are keeping it simple so that when you search for anything using Google the results you are given, are clear. And they are giving the websites ranking on the first page the most optimal opportunity for the user to click through. Google have never been design heavy for their own search engine and don't need to be. They will always focus on development and the mechanics of Google.
As for ads, YES you can differentiate it cause it has a word AD near the title.. People just are not use to change.. Well I guess google is targeting the new generation..
Its Google and we cannot do anything. We will keep on looking these fonts for next few years and start liking it.
The #1 company in the world (beyond more than just $$$) knows what it is doing. Their #1 revenue stream = ads. Natural results = nothing to them (except a way to suck you in). Make ads look like natural results = more clicks = more money. Simple as that.
Honestly it doesn't bother me, I actually think it's great because not everyone have a great eyes sight as I and some of you. My mother had hard time trying to read Google as she wears glasses and still find it difficult to read but now she could read them. I believe the meaning of Google change the size and the font is to make it suitable for everyone instead of just some of the people with great eyes sight only.