We have sent this through 3 different developers hands and we have not yet recreated your problem. I believe the problem that you may be experiencing has already been fixed but not released to the public at large.
So let's recap a few things on how the BBS actually works. A unique instance of a BO is created for each row that is shown within the result set. Each of these unique BO instances inside of the BBS uses a shared data table. So there is only a single copy of data. This is done intentionally and is no different than a collection with item objects internally. However, we did recently fix a bug where the BBS was not releasing all of the handlers of the internal BOs which could cause a memory leak under certain conditions. We have released this only to a couple of customers and we will release to all in the next 1.6.7 beta. The reason we have not released this to all is because all of the partials of the business objects will need to be rebuilt.
We will send you a copy of this build sooner than the initial release, but it will probably not be until the end of this week or the beginning of next week so that we can go back in source history and see if we can actually reproduce your problem to see if this will actually address it.