I have used both close in breeding and line breeding and have found inbreeding to be the best tool for quickly establishing a type of dog, and recognising any faults which may be present, showing up any hidden recessives and generally fixing the best points in a particular line of dog very quickly. Im an impatient person so linebreeding does not suit me, I like to know whats lurking in my dogs genes and I like to know as quickly as possible.
The main thing about inbreeding is that If you are going to use this method, you need to have a very cold objective eye for the stock you produce and you have to be able to recognise when a breeding programme is successful, and when it is not.
You need to be able to know when a breeding programme has failed, and when to call it a day and go back to the drawing board.

Once a type has been established by close inbreeding I use careful outcrosses and line breeding to continue the line without losing litter size and fertility as close linebreeding over many generations can sometimes affect the dogs reproduction, if inbred too much they may only be able to breed a few times in their lifetime or only produce a couple of pups. The most important thing with in or line breeding is a very extensive knowledge of all the dogs in the pedigree of the dogs being used, they must be more than mere names to you, you have to know their temperament, their faults, their good points etc, which is why it is always advised that only experienced breeders use this form of breeding.

I think it depends on the breed -how big is the gene pool and how 'true ' to type the breeder wants to stay
My Murph has a father daughter mating on one side and thats ok as long as its only the once and not three or four in ten generations .
carefull and well thought out linebreeding can be a good thing and keeps that particular line of dogs true to form -so its not always bad IMHO of course