problem with link building, is this - too many SEO spammers from foreign countries doing form filling. The sites will boot them so fast, its pointless nowadays, and to get on anything of quality is next to impossible, and the stories of super-seo boyz is bs.
Paying for links isn't bad, after all Google sells them via adwords, so their guilty of the biggest crime of all.
Links should be:
Quality - this means on websites that have respect, traffic and content. Its users are targeted, knowing they'll find what they need quickly and avoid all that clutter you don't need at that time.
Never buy links for links sake, many think a link-profile is about 50k of links like its a twitter account - No! twitter lets you get away with this, but building links the twitter way, is asking for trouble and you'd never do it anyway as the kind of sites that have 50k of links aren't normal anyway and clearly the average biz site isn't worthy of such mass due to zero content - so unless they have 20'000 pages of unique content, their buggered basically, you got to be a certain type of site to attract links and even they get lots of low quality links pointing their way, but just more top-end links too, which is the aim of good content.
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Link-building relies on paid quality, or you'll not get onto the quality sites. So many think they can talk or spam their way onto such web quality - I laugh at that as its just ridiculous to even think that.
Why would a huge site that probably has 200k of links or more, let some little 20 page effort swell its pages, when they can charge ££££ - it doesn't make sense to own a beast, then let everyone take advantage. What starts off as totally free, must go paid once its quota of content/users maxes out - it will go paid for sure every time, then kiss goodbye to free link heaven as most models leave out extra options, cannot get that big or are the wrong model/type to attract enough traffic.
I don't believe in the super-seos and this negotiating cobblers to build link profiles, its lies as I explained above. I checked the links of one in-demand SEO and the links were all naff.
Before you buy links, you must find out more information, you must! Form filling isn't the way, the form cannot talk back... but link buyers won't pick up the phone or email to get the facts, they think spamming is the answer.