A site called NONOFOLLOW has sprung up, providing 12 reasons against the use of the “nofollow” tag. The first and most obvious reason is that “nofollow” does not prevent comment spam, though that was the impetus behind its development.
Robert Scoble has a post in support of the tag in which he refutes each of the twelve reasons, with a pretty lively comment section both for and against.
It does seem that given substantial opposition to the tag, its creators are somewhat glib about the dissent, with Robert really basing his support on the benefits to him, as opposed to the upside or downside for others.
The nofollow tag does not block comment spam for you and I; it makes it easy for Google to block it. Nofollow applied to all comments may limit my ability to find interesting blogs in the future. And though it is great to see competitors work together, the tag was developed with little consultation.
The concerns need to be aired and not just dismissed, if only to guarantee that we do better next time.