Not just MKUltra - there is a long history of what I would describe as "shockingly unethical" experimentation in the US. The US Government (usually military) is probably the most common actor and/or funder, but they are not the only responsible parties.
This is why a lot of people (myself included) take a hard-line position of any kind of testing involving humans. Yes, it's often a waste of time to run many trivial experiments by an IRB first, but history has shown that some people seem unable to make this kind of judgement call probably. Really, in many case, an IRB simply serves the same purpose as assert(3); it's a "sanity-check". Like all sanity check, in theory it shouldn't be necessary, but history shoes it's worth checking anyway.
If the IRB regime had existed in the 40's, I doubt it would've have stopped this and other experimentation.
IRBs are effective at checking back everyday scientists. I somehow doubt an IRB panel would be need to be consulted by someone powerful enough to have the authority to load a crapton of bacteria onto a boat and spray it into SF.
Of course it wouldn't have stopped everything, but it would have helped - probably a lot. When everybody is getting their 3rd-party stamp of approval, those that do not are a lot more conspicuous.
Also, one of the steps in a typical IRB process is to sanity catch mistakes. As mentioned in another post, the people spraying bacteria over SF probably believe they were doing a "safe" experiment about dispersion properties. In an environment were it was regularly expected use an approval process, there might have been a chance for someone with biological knowledge to inform the experimenters of their error.
