I am planning my monitor mount now as well...
A proper glue joint is stronger than the wood its holding together, and the wood is most likely to split if anything breaks - not the glue joint. Look at every Gibson type guitar thats been decapitated, never a nice clean joint break. The screws you'll use are essentially there the help clamp the wood as the glue dries. I always thought that screws would do more if used, but then I got to talking to a cabinet maker friend who asserts that screws won't do as much as I think. The screws probably go 1/2" into the sides of the cab, and the first lil bit of that tip wont be biting into material. If terribly worried and want to use screws to reinforce the piece after the glue dries, I would consider using some small washers on the screws to add to their effectiveness and spread out the force, taking more to rip out the screws.