Google is not like yahoo and bing , because it only work on fair basis. In other search engines you can pay and get high rank unlike Google. If you are an SEO person than you must have idea about Black Hat SEO and White Hat SEO techniques. Link Exchange considered as black hat SEO, but why? The reason behind it is the division of PR between the parties. Google work on fair basis and any technique which vanished these fair meanings considered as Black Hat. Let me tell you about the PR division.
F(x) value of link juice transfer when site link to another. Page rank is like worth of your site and a part of it contributes for every outbound link of your site. For every dofollow link juice transfer , this is the reason why no one allow to place dofollow link on site, blog or any type of web page.
When site A first place link on it for site B, page rank of B will be up when search engine crawled it. Now the link from B to A will have more link juice as the Rank of B is up. In this case B is getting less than A.
So link exchange seems to be link division on equal basis but it is not actually.
There are some other disadvantages of link exchange. Like when exchange link from non relevant site there will be no chance of traffic but only the waste of your own link juice. Bulk link exchange will triggers search engines that site having some un natural behavior.
Link s the partners place to show without no follow attribute but later they make links with nofollow attribute. Which give you no point of placing link on them.
So be precautious when you are using link exchange technique for your site. For Professional SEO services consider the advice of experts.
I Shumail Ayub, an SEO expert. Working as SEO analyst in CuttingEdge Projects the leading business consultants in Leeds, UK.