I say come january 18th HN should either black out, or focus discussion on SOPA entirely in solidarity with reddit.
HN is a niche community with members who have a much greater capacity to influence the outcome of SOPA than a general populace. In some sense, a black out would inhibit the community's ability to affect change with respect to the issue.
If every active member of HN pledged to spend their available resources on the 18th towards working on SOPA, I suspect the outcome could have effects reaching further than even the championed reddit black out.
It's mostly a matter of deciding to place our money where our mouths are and collaborating effectively.