Your own list illustrates how pointless this sort of proactive activity is: in most cases, few or no new answers were posted regardless of whether the questions were protected. Indeed, the most-answered question of the lot was immediately protected.
It's not the raw traffic that creates the problem. It's traffic coupled with a question that begs for participation. Ars has its own forum attached to these, there's no pressing need for readers to come here to kibitz - unless the question itself is crying out for yet another answer...
Sometimes this is unavoidable. Questions that, within the rules of the community can only be answered in a narrow, controlled fashion may inadvertently imply a much broader scope to outsiders who don't know or don't care about the community norms. Protect is useful in these situations, where every n views will tend to generate m poor/spam/non- answers.
But these tend to be the exceptions, particularly on a site like this which doesn't really go in so much for discussions of tools or hardware or other spam-friendly topics. Protection here should be reserved for those cases where a good, answered question is attracting a large volume of noise / meta commentary from new users.
If you want to pre-emptively do something useful to forestall noise on questions, then edit them. Get rid of bits that implicitly invite any and all opinions, tighten up the scope, focus on making the question reflect its best answers rather than aiming for a big tent that welcomes all participants. Not only can this reduce confusion for outsiders, it can also benefit the folks already on the site who wouldn't be affected by Protection anyway.
Effects of Ars
I'm counting roughly 192 questions that've been linked to from ArsTechnica over the past 2 years that Sam's been doing this. Could be a few more or less; there's a lot of cross-linking, and I might have missed a few related questions - but this should be the vast majority of all questions that've been linked to. You can view a list here if you're interested...
First, some basic stats on how these questions have aged. Out of those 192, 31 are currently closed and 61 are currently protected. The average number of (non-deleted) answers is 12, the average # of deleted answers is 2.
Now... How they fared after being shared. I'm going to look at this from two different angles: a simple look at the number of answers attracted that would have been blocked by Protected status (had it been applied) and a comparison of the answer distribution before and after.
If all of the questions in that list had been protected prior to being shared, a total of 55 answers would have been blocked.
Of those 55 answers, 18 scored less than 0 and 16 are currently deleted. 23 currently score > 0.
Needless to say, these were posted to the 131 questions that weren't Protected.
Of the 2578 answers posted before these questions were shared, 2019 are currently scored > 0 while 211 are scoring < 0. 219 are deleted.
Of the 124 answers posted after these questions were shared, 60 are currently scored > 0 while 33 are scoring < 0. 23 are deleted.
As I noted in the first section, it's clear that Protection has relatively little effect on these. This jibes with my observations elsewhere on the network: trying to predict which questions will attract crap answers based purely on traffic is exceedingly error-prone; other heuristics are needed. Which is why we implemented better heuristics, based on observing which questions actually benefited from Protected status.
The % of not-useless answers posted after sharing is considerably lower than the % posted before; this shouldn't be too surprising, given none of them were new or unanswered. The % of not-useless new-user answers posted is lower than the % from existing users, but the volume is considerably lower.
Reserve Protected status for questions that are attracting noise or abuse from new users. Protect is not a prophylactic.