You have seen every kind of seo trick, which has been trashed by the search engines. Though all the measures were taken to keep search engine results healthy and less manipulative.
Now, the question comes about the blog commenting future – as this is the only easy way to gain backlinks – will search engines trash it sooner or later.
My idea is they will never ever do that. But don’t think that commenting on the link-farms blogs or no-value blog will bring you value. It will not land you anywhere. You need to search for the quality blogs – which accommodates only ethical comments – not spam.
Why Search Engines Will Not Trash Blog Commenting
Reason is simple – search engines don’t want to risk their own business. Look this way – search engines rely on content and if they pose some very rigid restrictions on blog commenting – it might damage the growth of blogs – which are largely due to comments.
Therefore, if the blogs will be less – there will be less content and less content means damage to search engines, so they will never ever pose any rigid restriction to blog commenting.
Till you are posting the ethical comments, which can be crawled by search engines – you are on the safer territory with blog commenting. The moment you post the spam – your website/blog will be degraded in search listing and the worst part – it could even get de-listed.