And this provides liquidity and broader distribution. If it increases prices, its likely that its just because there are restrictions on the *source* either real (elephant ivory, dodo skins) or manufactured (oil! diamonds!). If there are limits, these "middlemen" do indeed bid up prices, and when they do, they create incentives and opportunities for other suppliers to enter the markets.
One interesting bunch of service middlemen are those who deal with speculation. For example, if they think the supply of oil will change, even if it hasn't changed, they can cause the market to react. This creates nothing tangible and can even take stuff away, subjectivity. They act as service middlemen that allow money to be made betting on the point spread. One can't allows tell cause and affect, since these middle men could be working for the people who need them to help make money.
Middlemen are essential to creating efficient markets. There are many people involved in markets who "add value" to the delivery of products and services, and their value may not be obvious.
It might be fun to think of them as "a bunch of mindless jerks who'll be the first against the wall when the revolution comes," but they really do make the economy go.
In my opinion, the biggest source of problems in laissez faire markets is that it is indeed easy to corner supply--sometimes with the assistance of corrupt governments--and thus create imbalanced markets: Government does indeed play an important role in markets by ensuring that monopolies do not develop and the number of participants is large enough to ensure competition.
You don't need to make up terms to find problems to be fixed:
As discussed earlier in this thread, this is a non-standard definition of "demand side economics". There is supply and there is demand, and they interact to create markets. The term "supply-side economics" refers to the activity of government lowering taxes to free up capital for increasing production as well as to drive consumption. "Demand-side economics" (which is a little-used derogatory colloquialism to economists who more frequently refer to they concept as "Keynesian Economics") is also a government driven policy of increasing government spending to spur demand directly. Neither term is used outside of the discussion of government policy.
Demand side economics...
There really are a lot of good books out there on Economics, and its much more interesting to study it than to make stuff up that's been long-since figured out in quite a bit of detail!
Here's a great one to start with (I haven't read it but its been recommended to me by friends: Naked Economics: Undressing the Dismal Science http://www.amazon.com/Naked-Economics-Undressing-Dismal-Science/dp/0393324869/. There are oodles more though! Browse around!
Economics is extremely useful as a form of employment for economists,