The biggest thing that annoys me in modern gaming is that everything has to have a bloody multiplayer component, to the extent companies will rape fantastic single player franchises just to inseminate them with one.
Couldn't disagree more. There is almost no game that isn't made better with a strong multiplayer component. The problem, of course, that a strong multiplayer component is both /hard/ (and there are lots appealing traps that turn out to be poor decisions during the design process) and an investment few companies are willing to make unless the game is /dedicated/ to it, and that sucks.
Secret of Mana was a better game for it's multiplayer component - So was the original Baldur's Gate. That these were single-player franchises did nothing to take away from the fact that they were great multiplayer experiences, from the get go! Portal certainly showed how awesome good multiplayer is when added to a single-player game. All of these, every one, are better for the addition of multiplayer.
But that's because the multiplayer worked with what the game was offering. You CAN do a multiplayer version by changing the game and still get something good out of it - See: Fallout Online - but it's hard, and many companies seem to be really, really bad at it.
The problem is not the addition of multiplayer, it is the addition of BAD multiplayer.