Originally Posted by Black All Through

If you are using the sites/blogs to gain ABC or ABCD hardlinks then you should spread them on as many IP's as you can, this will get you more trades from the same webmaster. While for the sites/blogs you are doing seo for the IP matters if your getting links back from the same sites in bulk. Not always, but very often Google will figure out whats going on and you could get screwed. However it's a little more complexed than that and if depends really on what seo strategy your on.