My site (wrongly but still) has a pagerank 8 and use to get up to a thousand hits by google a week. Now it gets about 20. Im not sure anyone truely knows how googlebot decides who to spider and how often. Almost seems random, like it picks URLs out of a hat. A very, very big hat. Possibly with a brim, possibly a tophat, possibly a bowlers hat. Mabye its even an old NCSU green bill cap, mines all nasty but they probably keep it in a clean room.