the main drawbacks to client server networking, would have to be:
Cost (they are very expensive to initially set up, as well as to maintain.)
Reliability (if the server goes down which can happen if the system is not kept up to scratch, or is being over worked, it brings down the whole network )
Additional users (it can sometimes be difficult to add new workstations to a client server network, simply because it would of been built with the power to operate with the initial amount of workstations on the network, by adding workstations you are straining the resources of the network, which will slow down the network, thus meaning in order for the system to be able to cope hardware may have to be upgraded resulting in more cost.)
finally they are not really suitable for smaller businesses because of the cost and size of the operation, initially a company should probably use a Peer-to-Peer network as they are alot cheaper and cost effective , they are also much simpler but have limitations as to how many computers they can have on the network, also most problems that occur on a Peer-to-Peer network can be solved simply by Googling the symptoms