On promises made by marketing

In a large software organization, like in all large and complicated mechanism, friction always occurs at the interfaces.To overcome it, multiple communication lines are often erect between different functions. Take the army for example - while there's communication up-top, between the generals, often there is a lot of direct communication in the middle ranks and even more in the lower ranks. Doing otherwise would cause havoc on the battlefield - the air-force might bomb a location, but the message from the ground forces scout (that the target is long gone) is still en-route through the "official" channels.
In a software organization however, there's very little communication between the R&D department and the marketing department at the low ranks. Only the top managers - product level and upwards usually - meet with the people that actually meet the customers. This is usually excused by the need to "free the low-ranking R&D people (read-  the developers) from business concerns".
However, this lack of communication causes strange scenarios, where the marketing people don't really know what the product can and can't do and, even worse, don't know the future directions that can be traversed. Sometime only a tiny change in the code is required to enable a huge benefit (and a large increase in sales) for the customers. However, this request for change never comes to R&D because it's filtered by the marketing devision.
The same issue, only in reverse, occurs in the R&D department. Sometime we, developers, labor for days and months to enable a complex feature - that ultimately is used only by a small fraction the customers. Even more often, we over-develop - create a feature too wide in scope and too sophisticated - when the customer really just wants the simple thing done (usually over and over - and could we please provide some automation for that?).
Probably the worst sin of the marketing devision is committing to something that can't be delivered - or can be, but with great costs (development, architectural or performance). This is not done out of spite, though the complete effect does sometimes seem like the something done by an evil gremlin. The marketing devision truly wants to make the customers happy - but they lack the specialized knowledge the R&D personnel have - how exactly the product works. The worst sin R&D can make is barring (or even removing) features without really understanding the impact on the customer base. Again - not out of spite, but simply because no one has any idea.

The emerging pattern is of two disparate organizations - one dedicated for the "beauty and pureness of code", the other for "placating the customers" - while none is really dedicated for "create a product the customers want to use". This pattern especially visible the more "technological" the product is - the harder it is to actually understand the underlying logic.