There have ben a couple of ideas thown around here, which I would like to comment on if I may...
Xue Sheng said "Just a note.....Traditional Martial Arts were the RBSDs of their time."
I would actually argue against this a bit. I would say that original combative arts were, in the main, the cutting edge of combative technology at their time... but that is not the same as saying they were the RBSD's of their time. The main difference between them is what I have heard refered to as "the human element", in other words, the who, when, where of the situation. This is where RBSD systems excel, for the modern world.
The human element in a classical system (and here I am refering to the older arts, not those created in the last century or so. I mean no offence to more recent creations, but we'll deal with them another time) is very different to the human element found in (predominantly) Western countries today. The types of attacks you may encounter are very different, the types of weapons you may face are very different, the types of clothing you and your opponent may be wearing are very different. To take this from a Japanese Martial Art point of view (my background), a particular art may teach you certain strikes and grips whichare designed to utilise an opponents armour, or, for slightly later arts, their Kimono. These grips may not be available if your attacker is wearing a t-shirt, for instance, and there may be many more strikes available, or better striking weapons for you to use. And defending against a sword versus defending against a handgun give you very different situations.
TMA's have been developed for a variety of reasons, sometimes for practical use on the battlefield, sometimes for "street" type protection, sometimes for bodyguarding-type skills... but also sometimes simply for fitness (an exercise program), or spiritual enlightenment (rather than physical violence).
So while TMAs were the cutting edge, they were not really RBSD in the way the term is used today.
Omar B said "RBSD can go take a flying leap! It's a damn industry buzzword to sell to the ignorant. TMA works, has worked and will continue to work because nobody's grown an extra arm, leg or evolved some freaky new joint so they can throw a punch from some crazy angle. The same Kyokushin and Seido I learned was effective decades ago and will be for the rest of time ... if you are fighting humans that is."
This has been a common theme in this thread, basically "people haven't changed, hitting the throat worked in the old days, if you hit someone in the throat now it'll still work!". This takes us back to the human element. But there's a bit more to it than that.
Essentially, I see the argument that TMA training will not necessarily give you self-protection skills as coming down to training methods and an understanding of the changing nature of the violence that may be encountered. The changing violence aspect is the aforementioned human element, and that was covered earlier. But, to recap, the warriors and violent criminals of old Japan, China, and Korea attacked and fought in a different way based on various factors, including each of the above mentioned, as well as simple cultural differences (for example, in the West, we are taught [culturally conditioned] to not kick someone in a fight, as it is considered "dirty" fighting - the same cultural stigma seems to be missing from Eastern countries). This leads to very different methods of movement, which may or may not be culturally translatable.
So while people haven't (physically) changed much (there is some difference, if we want to get technical, in aspect such as height, and, to a lesser degree, ratio of limbs to trunk), there has been quite a lot of change in the cultural and social aspects of humans as a whole. We are now all very aware of Western Hands (boxing), whereas in older Japanese, Chinese, and Korean systems it wouldn't exist. This is of course just one example, but I'm sure you see where I am going with it.
Without understanding the changes in the violence which you may encounter, as well as understanding the changes which have occured from a social level (assault laws being a great example of this... I have lost track of how many times I have seen a TMA demo of a defence against a simple attack, say a double lapel grab, that is so overkill that the defender would serve large amounts of jail time whereas the attacker would be considered the victim), then your TMA system will not truly prepare you for todays encounters. No matter how much hitting someones throat works, if it lands you in jail, or if it requires a particular body weapon due to it originally being used against an armoured opponent and is therefore slow, obvious, or simply not the best weapon for the job, then TMA does have a fair bit to answer for when claims are leveled at them for being less-than effective.
The other side of TMA not being effective comes from the training methods themselves. I am not going to say which methods are good, which are great, and which need to be re-examined, as that is not my place in anything but my own school, but I'm sure you can understand from what I have already said that only training old-style movements with no regard for the effects of adrenaline, no understanding of the effect of your actions, and thinking this will work can be a little self-delusional.
That is, of course, easily rectified if the above understandings are present. And that is where RBSD comes in (when done properly).
Its still water, but the method of getting it has changed. 
