I think 99% of email users have not been adequately trained in why or how they should report spam, and even if they were I think most of them would still not care enough to actually do it with any regularity.
When pushed many may acknowledge that they know it exists, they will probably even be able to find the button when asked if given a chance. But they won't remember to do it when they see spam, they'll just ignore it and move on to the messages from people they know.
After all, the real goal is giving people a better, more relevant experience, detecting and removing spam is just one facet of that. Whether it's email or search.
However I don't think it's as simple as changing the button text. Even a process driven UI, like a wizard style interface where you have to click next to progress through each step might work, but users very quickly become immune to dialogs. They don't read them, they just evolve the actions that get them to their goal the fastest, and the users goal does not include reporting their spam.
She's been applying it ever since quite efficiently.
Shift+e for "report spam" would be perfect. Same key, just a bit chorded.
With search results, the spam is more often than not Made for AdSense sites that the average user doesn't realize are pure garbage. Then there are the mass-produced content sites like eHow that most technical people realize are worthless, but the average user loves. It isn't often you see Viagra sites popping up in searches for woodworking. It does happen occasionally though.
So no, I am pretty confident a majority of users would not utilize effectively a feature like that.
I posted this as an entirely self-serving request for a way to make my results cleaner.
Also: If the majority of users do like eHow, then that's a sign it's not spam. But a lot of 'power users' consider it spam. This is an argument FOR personalised blacklists, not against them.
And when it's about search result. People are browsing and clicking through adsense filled "landing page sites". Most of them think that it's their fault that they couldn't find the thing they were searching for.