Excluding certain books may be a good idea if you're compiling a list for their general readership. Simply put, you don't want one segment of the market to dominate the list if they are particularly devout in their reading.

Likewise, you don't want people to know your sources otherwise it would be possible for people to create an artificial run on those booksellers to boost the profile of a book.

The important thing is to understand why they do these things, and figure out whether the list meets your needs because of that. If it doesn't meet your needs, use another list.