It's just the cliche of the moment. It means someone is putting "toolset" above "skillset." Buying stuff they don't need instead of training to use realistic tools effectively. Usually it is accompanied by the habit of decking oneself out in lots of tactical clothes (or BDUs), trying desperately to look like someone who's capable and deadly, without the training and skills to back it up.
Originally, the idea was spawned out of folks' general derision for the type of private security guards that often patrol shopping centers. Folks who have very little authority, but like to give folks the impression that they have a serious and dangerous job, and a few of whom may have adopted over-the-top outfits and equipment which help to flesh out a fantasy life of danger and bada$$itude. (Google "Gecko45")
No...just read this:
http://lonelymachines.org/mall-ninjas/ Danger, it is funny enough to make a grown man pee on himself. You are warned!
Nowadays the definition has expanded to mean anything that might be just a bit over the top, or an attempt to "buy skills," or to solve a skills problem through better/more equipment.
Simply putting a laser sight on an xD really isn't all that bad an idea, but you do need to understand what a laser sight can do, and what it can't. Ideally, you'd have a lot of training with your sidearm without a laser and then with one. Once you're good with the basics, you can use niche tools to expand your capabilities, if you still believe they will help you. Not really a Mall Ninja issue, but, like I said, the definition seems to be covering a lot of things these days.
-Sam
