In his farewell speech of 1961, Eisenhower warned of growth of the 'military-industrial complex' and the 'potential for the disastrous rise of misplaced power.' It was a speech he began working on two years earlier and went through 21 drafts - which perhaps indicated the importance he placed upon this. Originally the phrase was 'military-industrial-congressional complex' but the word 'congressional' was crossed out and did not make it into the final speech.
The dangers that Eisenhower spoke of are not new, George Washington in 1796 warned of 'overgrown military establishments are under any form of government inauspicious to liberty.'
Times were different back then - there was a Cold War - and Einsenhower would have been worried about the cost of an arms race with the then Soviet Union and given that it at one point it spent a third of its GDP on its military this was a significant worry. The NPR point out that
Before the late 1950s, companies such as Ford built everything from jeeps to bombers but then went back to building cars. But that changed after the Korean War ... it kept a large standing army ... [and began] a technology race with the Soviets.
And this was also echoed by former Secretary of Defense, Robert Gates, who in a speech in 2011 in the Eisenhower library said:
Does the number of warships we have, and are building really put America at risk when the US battle fleet is larger than the next 13 fleets combined - 11 of whom are our allies and partners?
This, then is an argument for cutting military spending. However, going back to Eisenhower's speech, as a warning it appears stronger than this. Perhaps more in line with his warning were the revelations by Edward Snowden on the extent and range of the surveillance by the NSA on its own domestic population. In a sense, everyone was now a suspect. The amount of information that the FBI had on Martin Luther King pales in significance compared to the kind of information that the NSA has on each and every citizen. Laws that were intended to protect citizens from unnecessary, intrusive and illegal surveillance were outpaced by technologies that were pushed through by a political will that believed in 'total information awareness' and 'full-spectrum dominance'. It's probably apposite to note that the NSA did not go to congress to gain sanction for this because more than likely, they knew they had a vanishing chance of getting it.
It's these kinds of abuses of the power invested in the 'military-industrial complex' that Eisenhower was warning of.