A lot (ifr not all) of their house-brand frames [i.e. Motobecane; Mercier; etc.] are simply leftovers or additonal runs of older name-brand frames. Like: The BD bike I used to have, had an older model Fuji frame, simply rebranded, and with different components.
Generally you get a good deal for the price with BD- especially with the lower-end bikes...but there sleazy marketing (i.e. the perpetual "sales"; and making believe that their house brands are actual bicycle companies) really turn me off, and make me hesitant to recommend them to people.
For those who live in areas where there are few or no LBSes, or where there is a scarcity of decent used road bikes, BD can be a decent option...but like anything else, the value of their deals can vary from deal to deal- with some being not so good; and if you compare their prices to what you can often get a good name-brand bike for on winter clearance or the previous years model...their deals start looking less attractive.