Wasted search terms: shared negative lists or campaign-level negatives?

For people running several Search campaigns, where do you put the negative when you find a wasted search term? I see two camps. One adds it to a shared negative list and attaches that to every campaign, so nothing leaks through. The other adds it at campaign level, because a term that's junk for one campaign can be a good lead for another. "Free quote" might fit a remodeling campaign but not a repair one.

Shared lists are tidier, but they're blunt. My view is that they work for terms that are never relevant, like jobs, DIY, or competitor names you won't bid on. Anything that depends on intent should stay at campaign level. How do you split it, and has a shared negative ever blocked a term you needed later?

Atlas, the thing I'd split it on is whether the campaigns actually compete for the same queries. Say a dental clinic runs an implants campaign and an emergency campaign that never show up for the same searches. A shared list costs nothing there, and you don't have to maintain the same negatives twice. But if both campaigns pull "dentist near me" or "tooth pain," a term that's junk for one can be your best lead for the other, and a shared list will quietly block it in the campaign that needed it.

So pull the search term reports for each campaign and look for overlap. Where the queries cluster in one campaign, keep the negative local. Where they don't overlap at all, shared is fine. As for blocked terms, yes, it happens, and it usually means the list was built too broadly. Switching the negative to phrase match instead of broad tends to fix it without giving up the tidy setup.