defanjos - 5:23 pm on Dec 18, 2010 (gmt 0)
This happened to me a couple of weeks ago, if it wasn't for Google's warning I would not have discovered that one of my shared hosting accounts had been hacked. I am very glad they did it.
The reason I would not have discovered it easily, is because they did not hack my existing pages, they uploaded a bunch of new files to the sites.
By the way, once you fix the problem, Google gets rid of the warning fairly quickly.