Tarzan, I`d say it`s impossible to hurt the rankings of an established site by placing spammy links to them however it`s certainly possible to hurt the rankings for some time of a new, not established site that hasn`t yet gained Google`s trust.
What would be a very bad thing to happen to a brand new site without authority backlinks? You`re right, massive amount of unrelated, sitewide spammy links. I`d say such site would be sandboxed pretty soon.
cheers