Our instant reaction was that recyled materials are always better-
-waste disposal of building materials is a huge problem and re-using eliminates that;
-the embodied energy required to make them and transport them is already invested;
-even the most eco-friendly materials have some carbon footprint in their manufacture and transport;
-the money you spend goes to a good cause;
-in many cases, they don't make'em like they used to- doors, trim and other building components are heavier and better than the stuff made today. Even bricks can be made from wonderful clays no longer available, fired longer and harder.
-cleaning old building materials is labour rather than equipment and energy intensive- people have to pull the nails and chip the mortar. Instead of paying MegaCorp and Home Depot to make and move huge quantities great distances, you are supporting the local economy and creating entry-level construction industry jobs.
On the other hand, in some cases it is better that they don't make them like they used to.-trim and doors are probably covered in lead-based paint- you don't want to leave it but you don't want to breathe it while you strip it.
-asbestos, the wonder material, was used in siding, tiles, ceilings and pipe wraps.
-concrete and brick was often made with cinders from coal furnaces (In our city it was used as fill all over town) which is chock full of cadmium, lead and other heavy metals.
This is where it pays to get green and socially responsible- insulation, windows, electrical and plumbing is all better new if you go for the right stuff. The old stuff will use more electricity, water and not be as effective.
Until recent times, there was not even a question on this subject- if a building came down you recovered everything. Nails were too valuable to scrap; In Europe, stones have been re-used for millenia; when in University this TreeHugger worked as an archeological draughtsman for a book on a dig in Jerusalem, where the stones had been re-used to build different buildings six times in 1500 years. As metals are depleted (see John on Peak Copper) and people are stealing lamp posts in Baltimore for the aluminum, recycling will be not only the first choice, it may be the only choice.