I have repeatedly argued for a departure from pure Bayesianism that I call "quasi-Bayesianism". But, coming from a LessWrong-ish background, it might be hard to wrap your head around the fact Bayesianism is somehow deficient. So, here's another way to understand it, using Bayesianism's own favorite trick: Dutch booking!
Consider a Bayesian agent Alice. Since Alice is Bayesian, ey never randomize: ey just follow a Bayes-optimal policy for eir prior, and such a policy can always be chosen to be deterministic. Moreover, Alice always accepts a bet if ey can cho
And here I thought the reason was going to be that Bayesianism doesn't appear to include the cost of computation. (Thus, the usual dutch book arguments should be adjusted so that "optimal betting" does not leave one worse off for having payed, say, an oracle, too much for computation.)