My top search phrase is a single keyword that relates to a major topic of my site. However, it represented only 0.4% of my August search referrals from Google. My August server logs show 796 search phrases that contained that keyword and probably several hundred more that didn't contain the specific keyword but were about the topic.
I do rank high for that single keyword (#3 out of 41 million), so my experience tends to support your observation.
Given the sheer numbers of pages for any major search term, it would be understandable if users were getting savvy enough to search on "widgetville hotel rooms" or "widgetville tourist information" instead of just "widgetville," or on "widgetco wc-1 camera reviews" instead of just "widgetco" or "wc-1." And if multiple-word searches really are a trend, they should make it easier for Google to provide search results that better fit the user's needs--in some cases with a mixture of "Google Universal Search" results, and in some cases with traditional, plain-vanilla Web search results alone.