What you're describing, except search, are all "moats"[1]. They're all ways in which Google monetizes and generates revenue. Any threat to their bottomline has to come from people getting access to information in other ways: native mobile applications, Facebook's walled garden, television etc. To their credit, they saw the mobile juggernaut coming early unlike Microsoft and they dealt with it effectively, ditto for browsers and email. They did not deal with social that effectively. In each case, it was their ability to foresee an information flow paradigm and get on top of it. The argument here that can be made is that they're no longer that force that can monetize new information flow paradigms and that FB, Amazon, Apple are eating their lunch in some ways and whether they can make money without new sources of income (their new bets have not paid off yet). Whether this argument against them is stupid or thoughtful, the fact remains that this is a point that has been raised - not how good their products are, but how much money they can make, which is something a for-profit business must consider.

[1] http://techcrunch.com/2011/03/25/search-googles-castle-moat/