Back when I was a kid one of my weekly high-points was watching the original Twilight Zone (yes, in black and white). Many of those episodes started off with Rod Serling stood slightly off camera to the opening scenes, smoking and uttering the immortal words: "Submitted for your approval ..." as he whisked the viewer off on to some strange parallel reality where weird and wonderful (and sometimes scarey) things happened. With that in mind ...
"There is a fifth dimension beyond that which is known to man. It is a dimension as vast as space and as timeless as infinity. It is the middle ground between light and shadow, between science and imagination, and it lies between the pit of man's fears and the summit of his knowledge. This is the dimension of imagination. It is an area which we call the Twilight Zone"
If you've ever had to buy a car (or even a house), you probably know how things go in our world. You first decide what type of car you want (make, colour, cash range), then you look for a dealership. Next you visit the dealerships and, depending upon how good the sales guys are, may even reconsider everything you did in stage 1, coming away eventually with something you didn't evision when you first started (but hopefully something you still want!) Relatively painless. If there are any problems with the car within warranty, you go back to the dealer and they fix them for you. In all likelihood, if you get good service you'll probably keep going back to the dealership even when the warranty expires. Plus, if you choose the right type of car, the dealership is the manufacturer, with the obvious benefits that affords.
Now let's pay a visit to a strange alternate reality where things aren't quite so simple. In this world you go to the dealership and they tell you that the car you want isn't available as a single item to buy. Unfortunately in this world you have to choose all of the individual components yourself (wheels, engine, colour, brakes, airbag, ...) But not only that, you have to deal directly with the individual manufacturers in the way the dealership did in our reality. The dealership may give you recommendations, but they only provide support for the chasis (for example). Plus, that's all they will provide cover for: if you have problems with the engine, you've got to deal directly with its manufacturer because the dealership doesn't have the expertise. Bummer. (It's left as an exercise for the interested reader to map this to buying a house.)
Now fairly obviously this parallel universe is not a very nice or efficient place to live. As a consumer the last thing you want to have to worry about it keeping track of which versions of the engine work in which versions of the chasis and with which versions of the electronics, etc. Plus, you don't want to have to try to keep track of any issues the individual manufacturers may report. If there were only a few components, then maybe it's something you could do, particularly if it were cheap enough. But it really doesn't scale. What you want is the ideal of the first universe: you get everything you need from a single place and let them worry about the individual components on your behalf. Even better if that single place actually developed all of the components themselves, because then they don't have the hassle of talking to other manufacturers. It really would be one throat to choke.
The same is the case in the computer industry. Back in the late 1980's and early 1990's it was a very regular occurrence to see people buying components and building their own (cheaper) PCs than the ones they could get from IBM or Apple. Yes they had the hassle of checking which components worked together, but the results were significantly cheaper than the commercial finished products. Some people even build their own components from scratch and sold them on much cheaper (very early open source?) But as the markets matured, we saw the arrival of companies such as Viglen (UK), Gateway and Dell who really pushed the price of entry level machines down so low that it became ridiculous to even consider building your own. (It's arguable that this effect also caused the premature death of Sun's Java Station - it was just far too expensive for what you got!) These days very few people build their own and are more content to go to a single manufacturer for the product, even if the individual components are sourced elsewhere.
In the software market, we saw a similar effect. Particularly around middleware stacks. Which are always evolving. Before the advent of open source, you had to buy your complete stack from a single vendor. There were a few exceptions to this, but on the whole you were left with little choice. It simply wasn't worth the price of trading one commercial component in a complete solution for a different commercial component (even if it was supported). Open source threw us into the alternative reality for a while because it really was cheaper (100's or 1000's of times) to do it yourself; and most of the time it just worked (tm). But as the amount of open source offerings increased along with the number of them that people found useful, the support problems grew for the end user (remember the car?) This made Professional Open Source a fairly obvious solution: go to one vendor for all of your open source requirements and let them handle the support, which they can do because they wrote the stuff in the first place! Now there are not many companies that can offer the entire stack in this way. Sure there are some dealerships that can offer you "support" (notice the quotes) for the stack, but when you look deeper you'll find that most of the components you need come from elsewhere. If you like the headache and worries that can cause, then maybe it's worth exploring. However, are they really so much cheaper (and better) than going to a one-stop-shop? It's hard to be objective, for sure. But at the moment the market is clearly showing that Red Hat/JBoss are the best place to go for the middleware stack: people who tried living in that parallel universe soon found out that the cost was detrimental.
We now return you to your regularly scheduled program.