tedster - 9:06 pm on Jun 12, 2011 (gmt 0)
It's really not easy to generalize about this. In the past week here we have seen reports that:
1. New links were followed by ranking drops
2. New links from strong sites created no change in ranking
3. New links caused partial recovery from Panda devaluation
And whether competitors can harm you or not is an equally ambivalent area. Google has long said that there's ALMOST nothing competitors can do that will harm you. They added the word almost quite a while ago.
And there has been quite a flood of this negative SEO for several years. It's not at all new, especially in the competitive niches. I was personally involved with a few instances where it certainly looked like intentional sabotage had worked - and a subsequent Reconsideration Request (with documentation) worked, appearing to confirm that.
However, I have not personally seen anything like this in 2011. It seems to me that Google has some kind of overall profiling going on for the appearance of new backlinks - and that profiling is getting rather sophisticated.
I still think that "almost" is the operative word, but I doubt that it's become easier to hurt your competition. The pattern I see is that it has become more difficult to sabotage your competition - but easier to hurt yourself!