Over the last few years I have become more and more aware of this phenomenon. It's not, i think, that is becoming more prevalent, just I can now see "carrot danglers" coming a mile off.
Let me explain. A "Carrot Dangler" is someone who promises something if you perform certain task or do something they need. That promise is of course never kept. I call them Carrot Danglers because of the following picture of a carrot dangling in front a person. No matter how much you try to get the carrot it remains a foot away from you. Always.
Carrot Danglers typically reveal themselves on the second dangle. That is, when you achieve your end of the bargain, a second carrot is dangled and the first promise is never made good. My advice at this point is: a) run or b) do no more until the first promise is made good.
In the IT industry you sometimes need to take a punt on a project, incurring an upfront cost with a potential larger payback down the track. This conforms to the old adage of low risk low return, high risk high return. These speculative projects have a high risk (you are working for a promise) and should therefore have a high return. If the Carrot Dangler's first promise is not made good, the risk has risen at an exponential rate (close approaching impossible). Continuing to pour money into the project is as good as throwing good money after bad.