The case for merging, and not destroying spam users has not been made in time, and thus the spam user at Gaming has been destroyed, and with it more than a year's worth of information about sites that continuously send spam our way, information that could be used for justifying more extreme measures like additions to site wide blacklists.
We've already used this information to collect eight links from two separate waves of spam sent our way from the same site that, had we been destroying instead of merging, we wouldn't been able to document. That enabled Rebecca to go with the blacklist. If you're a moderator anywhere in SE, you can see the transcript here.
Currently we're again under attack from another source, and if I was destroying and not merging I wouldn't be able to document: 1 2. Two links are bit too little to trigger further action aren't they? Except I'm fairly certain this site has spammed us before... but I can't verify this anymore, as we've lost all information about this.
Now, it probably says something when I only noticed the deletion of our Spaminator 7 days after the fact - over more than a year, we only accumulated something like 50 posts (I don't know if my fellow moderators also merged instead of destroying, though), but I don't know how to act more. Should we stop worrying and love destroying spam, or should we be a little more mindful?
This entire post is written on the assumption that spam is the lowest class citizen of the network, and thus has received the least developer attention ("just destroy!"), and thus there are no real analytics that are collected from destroyed users' posts. If there was something (waddayaknow, just the URLs) and it was simply not available to moderators, obviously many of the points made here would not be as strong. I assume that's not the case.
url:*offendingdomain.com* deleted:1(and keep the*characters for wildcarding the start/end of the URL) to see what it turns up. At least that's worked for me before on SU where I've a ♦.url:withbody:"wow gold"? Probably less reliable, but might help. Anyway, I'm not against merging spam users (I have done before on SU), but now we have the as-many-logins-as-you-like feature I think it might have the side effect of suspending the credentials that are merged forever, while also bypassing the usual suspension mechanics. I wonder if that might be something on the merge-users option that needs more examination.