Why don't you pick up the phone and call these people if you have issues?
Send them a freaking certified letter with return receipt expressing your concerns.
Sorry but why should he? If the network answers emails and AIMs from affiliates then why should someone have to try to track them down when they chose not to pay or reply to legitimate requests for information.
I am sorry but I have had very bad experiences of large networks shafting affiliates and I can tell you for one that there is NO recourse when it comes to trying to get your money if it is under $10k and are not willing to drop more than that on legal fees.
Are you aware that a network can just not pay you if an advertiser decides not to pay them for whatever reason? Are you aware that they have a clause in their terms that state that if you sue them that they can go after you for costs, so even a contingency lawyer can end up costing you money?
Running traffic through a network seems more and more pointless as you realize that they don't protect you and don't pay you at a whim and you can't do anything about it.
I for one am going to sue a "big" network that shafted me, but I have deep pockets, other people with lower budgets haven't got a chance. I'm owed only $6k but its the principal and not the money, no one screws me over!