I doubt it would harm you. I certainly don't expect to get headhunted through SO (my score is low 4-digits), but I will be putting the link on my CV - as I probably will my NH profile - I don't have any other online presence (no fb, no blog, no github, no li). And although my score isn't super-high, I don't spend a lot of time on the site. I'll ask a question from time to time, and a couple of times a week see if there's anything I can answer. Hopefully my profile will give a reasonable overview of my general competence.