If you have a website with a contact form, even if you only have 10 visitors a month, you probably have already received emails written in horrible english, coming from third world countries and trying to convince you to buy their white label link building services. They often use the argument that links are good for SEO, and offer to get any number of links to your website for ridiculous prices, such as 10$ for 500 links. And if you are tired of building your own links or think SEO agencies are too expensive, you may feel tempted to click on the send a quote button. Even if they are not just a spammer hungry for your contact details, there are many reasons why you shouldn't outsource your link building strategy to a cheap, third world link factory.
You'll be seen as a spammer
The first reason to avoid bulk link building services as the plague is that they just give your company a bad reputation. If you have a blog you probably are familiar already with the deluge of posts flogging fake designer goods, written in horrible english and going "thanks for ur post. Much interesting. Please visit my website with your own website link and that's what you'll get if you pay for cheap, bulk link building services. Do you really want your potential clients to think you are a potentially illegal or malware infected scammer website? Not to mention the fact that you may end blowing any chance of a blogger actually writing a nice post about you and sending business your way because your hired help spammed him before.
Google will think it's suspicious
Google uses links as a way of measuring the popularity of a website, and has stated clearly on Matt Cuts blog what it thinks of paying for that currency. Now, Google knows that sometimes things go viral, and a website can get a load of links from many different sources in a very short span of time. They actually don't mind that. However, if suddenly your website receives hundreds of low quality links from forum profiles, comments on blog posts and unknown article directories, all with carefully crafted anchor text… Well, let's say that would ring a few alarm bells wouldn't it? And when Google thinks something is against their terms of service they usually drop the offending party from the index or penalize them until you can prove yourself innocent. Not that you could if you had purchased the links!
Low quality links are quite worthless
Search Engines don't think that all links are the same. A link from a reputable site will be much more valuable than a link from a free forum post. Paying for 500 links may have a lesser total effect on your PageRank than getting a single quality link from a good website. And why are they worthless? Because nothing stops you (or any other business owner) from buying 500 domain names, installing 500 forum or web directory software and using them to build links to your website. Those links doesn't mean that anybody except for you think your website is valuable, and are on the eyes of the search engines totally worthless. So if you are buying low quality links you are wasting your money. Better spend it creating useful and high quality content that attracts links, or distributing high quality articles for article marketing.
They don't really care about you at all
A link farmer only thinks about you in terms of how much are you paying him. They won't try to get links that actually direct qualified traffic to your website (even if their marketing material says so) or care if they make you look bad by spamming links to your website in X-rated websites or link farms. If you pay in advance you risk never hearing from them again, and there's no guarantee those links won't be deleted by forum admins and angry bloggers after you have paid for them. Wouldn't it be better to spend your money choosing a professional marketing agency whose goal is actually getting you to sell more?
You get what you pay for
Look at it from the link building employee point of view. They are being paid much less than 1$ to get a link to a website they don't care about, written in a language that they may not even understand. Would you spend hours researching the best sites to place that link, or would you use automated software and spamming bots to try to get as many links per minute as you can, so you can make a living? You really cannot ask for working ethics and SEO knowledge from somebody who is being paid way less than any living wage to promote your company, along with a thousand others, and has strict link building targets to achieve if he wants to be paid.