g1smd - 8:57 am on Mar 20, 2012 (gmt 0)
No crawl spike noted in recent days, but I do see these from time to time. It appears that Google has a scheduled process that runs once or twice per year where they respider a huge number of URLs in a day. Often these include URLs that return 404 or 301, so Google is just rechecking they still return those responses.
Most of the time that I see a huge spike in crawl rate this is immediately (next couple of days) after making major changes or site-wide changes. The last time I saw this was a few weeks ago and this was after delivering "503 unavailable" with a retry time of several hours while a site moved to a completely new URL structure. A few hours after the replacement site went live (with redirects in place from the old URLs) Google started crawling and then accessed nearly all of the new URLs and many of the old URLs within the next 48 hours.
On a site with no work done to it in the last 6 months, and just a few minor edits to several pages during that time, there was a huge crawl spike about 6 weeks ago. At that time Google recrawled all of the 404 errors from the duplicate pages that were removed more than 9 months ago. It was an isolated one-day event, but filled the WMT crawl errors report up from just a few dozen entries to thousands.