This is an interesting, but logical, take on this. If your buddy who takes no bailout has a major problem (eg a caustic cocktail), he WILL be trying to take your bailout if he hasn't done a rapid ascent to the surface. This may then leave you without bailout again. I know that I could not personally refuse my bailout gas to an out-of-options diver (and watch him drown), and don't imagine they would take "no" for an answer anyway! If you want to carry enough gas for both of you you'll need a bigger cylinder, or two stages (at least). Much easier if you both take some!

Neil