It comes by many different names; bulk traffic, redirected traffic, pop ups, pop unders, and sometimes it is even called targeted traffic. But don't believe it.
Regardless of what it is called, it is all essentially the same thing -- junk traffic. And for good reason.
Most of the traffic you see for sale, especially on places like eBay, is considered to be very low quality traffic by experienced webmasters. The cost for this kind of traffic ranges from $5 to $15 for 10,000 visitors and $25- $90 for 50,000 visitors. With such low prices you can estimate that the quality of this traffic would be poor. In fact it is not uncommon for every single pop under visitor to result in a non-action - that is they will not buy or click anything on your site.
The reason is simple. They did not end up on your site on purpose, so they simply ignore your site. Most consider it a nuisance that they where there in the first place. If it really worked, then experienced webmasters would be buying millions upon millions of it everyday, and the demand would be so great that the prices would be forced sky high. That is what happens with real traffic that converts to sales, mostly PPC traffic from the search engines.
The best use for this kind of traffic is for things like banner impressions, and even that can backfire on you once the advertisers find out what you are doing.
There is little point purchasing 100,000 visitors to your site if not one of them buys your product, clicks your Adsense ad or makes an action through your CPA form. You are simply wasting your money. Countless webmasters have conducted tests with this kind of traffic with little luck when it comes to return on investment. In many cases it would only take one affiliate sale to make the money back on the traffic investment cost; however this rarely occurs due to the low quality of the traffic sent.
Why is this kind of traffiic so bad? The main reason is that it is completely untargeted, regardless of what you have been told by the seller. There is no demographic targeting or anything that would result in an increased chance of conversion. Some testers have stated that pop under traffic can work if there is a lot of it. This can mean purchasing hundreds of thousands of visitors in order to make just one or two sales. It has to be asked whether it is worth the money and effort required, or if the money is best spent elsewhere. Indeed, if 100,000 visitors were to be generated from a much more targeted source it could result in a conversion rate of 5% or more compared with a 0% conversion rate from targeted traffic.
People buy cheap traffic mainly because they are looking for a short cut to success - and it sounds like the answer they are looking for. If you still choose to proceed with a this kind of traffic campaign, make sure you track your statistics in order to confirm that you are receiving the traffic number stated. You should also ensure that the traffic provider has a money back guarantee if they do not provide the stated unique visitor numbers as outlined on their website.
It is best to spend your time and money on more reliable sources of traffic such as organic search engine traffic and pay per click advertising if your goal is to make sales.