When you make a search, below each link there are things such as
Cached, and Similar Results, to allow you to view further details about
a particular result.

I'd like to request the addition of a Report as Spam link to show next
to that, as well as a link such as "About this link", that will give
you details such as how many users have reported that link as a bad
result for a certain query.

Google doesn't have the resources to go through it's entire database
looking for spam, so how about letting the user do it? It might not
have to be enabled by default, it could be something listed in the
users search preferences, similar to language selection the safe search
filter.