Generally speaking the links can't hurt you unless the site that's linking to you is in a bad neighborhood and your site looks like a link farm (a site built to give links for the sole purpose of improving other sites search engine rankings) For example, if the site linking to you is a link farm and gets discovered by the google spam team becuase they link to a bunch of pharmacy sites that they have their eye on and your site looks like a link farm or looks like it was built to manipulate search engine results by selling links or giving links to other sites your site could get banned. No PR. No listings in SERPs. Seen it happen many times, a site gets reviewed for linking to a spammy pharmacy site and any other site it links to gets a free look over by the Google spam team. As long as your site is legit you have nothing to worry about.
the blog comments have been added no follow tag for each link, it means your link will not get any link juice, but you can get some extra traffic. Search google for "do follow" blogs list if you want help your site ranking.
This is not quite true. It does give a *little* juice, if it comes from a reputable blog/site/etc. Google even semi-admitted this (not that they need to, and they have an incentive not to admit it). But it's still nowhere near as effective as dofollow links.
agreed. actually, there are blogs with nofollow, but also with dofollow attribute - just install simple firefox add-on (I think it´s called "dofollow") and you´ll see it instantly, when you land on a blog
I think you're talking about the addon called "Nodofollow". It sure highlights the nofollow and dofollow links separately on a page instantly. You can enable and disable it anytime with a single right click and a left click in the menu. I love this addon.
I don't see why it would hurt seo rankings, I've never had any problems with it, and I get most of my back links from blog comments and forums.
One way links could help with various effectiveness degrees and the blogs comments have been counted on among the useful ways to build links.
I think he's asking if a competitor can harm him by posting a negative comment on a blog but linking back to his site. Ironically, I'd have to laugh and say that would probably backfire on someone and help your site. Let's say for example someone made a very controversial or harsh comment on a blog. It might start a huge argument/discussion of threaded responses and bring more attention to the comment that started it. I don't recommend trying this strategy with your own site intentionally because like I said, it can backfire on you too! However, the do-follow attribute means link juice will be passed.
No Follow comment in NOT USEFUL or HARMFUL in any way at all. All it effects is how much traffic you receive from those links, and what your those visitors know about your site ( from the anchor text ) that's all.
Blog comments are definitely good for getting link juice, but stick to relevant blogs and post meaningful and useful comments - so that the comments stay and you get valuable backlinks which help you build authority in your niche