One of my friend had lost PR of his 5 sites, Earlier he had PR4, PR5 and etc, Now all become PR2 or less. However, he did not add any new content or there are no more spammy things on the content. Regarding backlinks, He had got about 100-150 backlinks per month all are from good source.
But still, PR is lost.... It is a real wonder :confused:
However, I guess that, may be the content of his sites are used by others or etc. What do you warriors guess?