LISTEN FOLKS:
Here's the whole point the DEVS had, and have related repeatedly, concerning unpriced BODs in BOD Books. I even confirmed this at a town hall, though after the meeting (never got a chance to ask it during the actual questions session, in favor of some other questions that I asked first when called on)
The ORIGINAL INTENT was to allow people to store unpriced BODs in Books on vendors to ENCOURAGE PLAYER TRADING (as opposed to selling), as others can see what you have to offer, then contact you (At your home, via bulletin board or locked down books) to arrange the trade.
That one can store BODs in Books this way, and not ever actually trade BODs with other players, is just a matter of player attitude. It does not break any rules. AND, if one actually DOES need one of those BODs, and can catch the homerowner at home, you can STILL make the attempt to arrange a trade with him or her - which in and of itself IS the kind of player interaction the Devs were looking for, in the first place (the worst that can happen is someone telling you to go do anatomically impossible acts with oneself, unless you're in Fel or playing on SP or Mugen).