Do you mean by "intimidatory downvoting" something substantively different from the thing (or things) others have referred to as "retributative downvoting", "block-downvoting", "karmassassination", etc., in this and related threads? If so, can you clarify what you mean?
I'll explain how I use all those terms.
Intimidatory downvoting: Downvoting whose purpose is to discourage people from expressing certain kinds of views on LW by the threat of massive karma loss. (In particular, the threat of much more than they would lose just from having their comments expressing those views downvoted.)
Retributive downvoting: Downvoting whose purpose is to get back at someone who has annoyed or upset you, or whom you don't like for some other reason.
Block-downvoting: Largely-indiscriminative downvoting of a user's comments, whatever the r...
I'm just tired of the signal pollution, and would like to be able to use karma to honestly appraise the worth of my articles and posts, without seeing 80% of my downvotes come in chunks that correspond precisely to how many posts I've made since the last massive downvote spree.
EDIT to add data points:
Spurious downvoting stopped soon after I named a particular individual (not ALL downvoting stopped, but the downvotes I got all seemed on-the-level.)
One block of potentially spurious downvoting occurred approximately one week ago, but then karma patterns returned to expected levels. I consider this block dubious, because it reasonably matches what I'd expect to see if someone noticed several of my posts together and disagreed with all of them, and did not match the usual pattern of starting with the earliest or latest post that I had made and downvoting everything (it downvoted all posts in a few threads, but not in other threads), so I'm just adding for completeness.
Spurious, indiscriminate downvoting started up again approximately half an hour ago on Sunday (12/1/2013), around noon MDT.
Edit: And now on Tuesday, 12/3/2013, at 10 AM, I'm watching my karma go down again... about 30 points so far.
Edit: And now on Saturday, 12/14/2013, at 2 PM, I'm watching my karma go down again... about 15 points so far, at a rate of about 1-2 points per second.