These tastings must not have always ended well. What comes to mind is the Parkinson-inducing desmethylprodine which was discovered by "accident", although the chemist in question (Barry Kidston) tasted it on purpose -- he thought he was developing a recreational drug. But you would expect more chemists dying randomly, if they were tasting their lab contents at this rate -- but maybe I just don't know enough.

EDIT: Noticed that some comments above discuss the likelihood of random chemicals being lethal