On Sun, 24 May 2009 18:30:02 -0700 (PDT), muzician21
wrote:

I got tiles, premix thinset, "blue board" water resistant sheet rock
in preparation to replace a section of tiles in my shower stall.

Bad move. Premix thinset and "blue board" are not intended for wet
applications. For this application regular thinset and "hardibacker",
or equivalent, is a must. Neither are difficult to use and will last.
The
guy in that dept where I got the stuff at Home Depot insisted I don't
need spacers for the tile, that shower stall wall tiles are supposed
to be butted up against each other.

As others have said, if the tiles have the bumps on the edges spacers
aren't required. I'd use them anyway.

All the "how to" videos I see on YouTube show the use of spacers for
setting shower stall wall tiles. You think this guy just didn't know
what he was talking about?

Since he didn't tell you that "blue board" was a waste of time and
money, certainly.