I think Knol is too much like wikipedia for it to be a real threat to blog. As was said before, the only ones it will threaten would be the prolific niche bloggers, but even then I think they will be hurting too bad. Knol seems to be like material that could become a guide book type thing, where as those blogs are more of a personal news-y thing. I don't think Knolling is personal enough for me to trade blogging for it.