In the thread about the 'ranking delay' algorithm, I reported that a site of mine had continued to rank after I pulled my PBN links from it. At that time, it was somewhat non-meaningful, because the time frame was so short. Now, however, it's been nearly two months, and the site continues to rank. I had pointed about 10-12 PBN links to a site, and it jumped sharply within a few days. A couple of weeks after I placed the links, I pulled them. However - the rankings did not slide back to their original spot (#39), instead, the site continues to rank today in exactly the same spot that it was at the time I removed the links. It's jumped around, up and down, but is more or less stable. Whilst one isolated case is not conclusively demonstrative of anything, I am beginning to take the view that G 'remembers' links, and simply 'once having had' links from a powerful or authoritative source may be a significant ranking factor.