This sounds like a stupid question, but it seems to me that based on several debates currently ongoing, it is becoming an increasingly valid one. Two specific discussions come immediately to mind.
First, last week there was quite the kerfuffle over at TechCrunch over the actions of a competitor to a company reviewed by Mike Arrington.
(Pointless aside: I have noticed recently that Neville Hobson uses the word kerfuffle frequently and it has become a new favorite of mine, especially as it relates to the blogosphere. And even though this is my second mention of Neville today, he does not pay me a cent for the mentions — which is probably good since I’m certain he has more, better readership than I.)
In a nutshell, a company named Spinvox was reviewed on TechCrunch and offered a limited number of free accounts to readers of that blog. In order to claim the freebie, readers had to post their email address in the comments. Seeking to take advantage of the situation, a competitor named Simulscribe had their CEO email the same folks offering a free account on their system.
A vigorous debate broke out after Arrington slammed Simulscribe for "boldly spamming" his readers. Perhaps what really set him off was the subject of the SimulScribe email ("Free Trial from TechCrunch"). Some commenters argued it was merely a good guerilla marketing tactic, while others concurred it was blatant spamming. As it often does when the question of spam arises, the comments became quite vitriolic.
Now today comes news that Wikipedia is attempting to fight link spam on its property by instructing search engines not to pay attention to outbound links anywhere on its site (in tech terms, using a "nofollow" tag on all such links). Many are praising this decision, but others are raising questions. Nicholas Carr questions the move, however, and notes that others have concerns as well.
I wonder, though, if it could also have the effect of reinforcing Wikipedia’s hegemony over search results. The sources cited in Wikipedia, many of which are original sources, will no longer get credit for their appearance there, which should cause at least a little downward pressure in their own search rankings (hence providing a little more upward pressure, relatively speaking, for Wikipedia’s articles).
And even among those who agree with the move, some wonder whether there ought not be a way to separate the spam from the legitimate links. But inevitably a debate will arise over how to make that determination. There will be many cases where the verdict will be uniform, but in many others there will be dispute. At the end of the day, of course, it will be Wikipedia’s decision to make (as it is for all site owners), but the implications could well be broad for the community as a whole.
Ultimately, spam ends up being entirely in the eye of the beholder. Or as former Supreme Court Justice Potter Stewart wrote in a famous 1964 opinion where he couldn’t assign a specific definition for pornography: "I know it when I see it."