tedster - 6:31 pm on May 28, 2011 (gmt 0)
In WebmasterTools you can see the data for SERP "impressions" - that's another way of saying "exposure", and it's been in the reports for a long time, as well as being mentioned in many patents. Seems clear that Google does measure SERP impressions for the domain name as well as for individual URLs.
I'm convinced that getting a major jump in impressions after you make some kind of change can trigger a manual inspection. At the same time, Google may intentionally increase impressions to see what happens with click-throughs, as well as how that affects click-throughs to other sites in the rankings. For highly competitive query terms, the CTR threshold to beat may well be whatever the previous URL at that position was generating, rather than just some "absolute" percentage.