I'm curious to know this too. they must be charged for having x amount of links or something. it has to be about money.
Actually there are several reasons why you would be declined. For example imphpguru you are in india....Absolutely nothing wrong with that, but some merchants actually alot of them will auto deny people in your country and surrounding area due to high fraud. that is just one reason. another reason is maybe they think that just because you are in india your traffic base will only be in india which is ridiculous. Other reason why they deny is they are at quota for the affliliate base. some companies are only allowed so many affiliates. Another reason is they saw your web site and they made a personal desicion to deny you based on the quality of your site. Merchants are not charged x per link they are billed on payout. Like lets say I made 2000.00 with merchant x they would intern have to pay CJ or linkshare or whoever 10% of how much i earned. that is how CJ and other affiliate networks make their money.
There are many grounds for rejecting your application. One is location. The other one is that your website does not meet an advertiser's expectation.
They often have minimum requirements for sales in certain categories to accept you. If you've never made a sale or don't have a min. amount of impressions, you won't have any luck with some of the bigger publishers.
Not sure where you live but some publishers may have automatic rejection criteria in place. That's the case if you let's say are not from USA/Canada for example. If you really want to join the affiliate program you applied for try to email the affiliate manager - if any - and include your site and ask if they reconsider your application.