A common result of moving instructions through early processors at too high a rate to maintain laminar flow. Early cryptographic algorithms in particular were severely limited by such considerations, until the advent of modern pipelining algorithms vastly reduced susceptibility to data cavitation.
As a point of historical interest, the "dataflow" paradigm in programming originated as an alternative approach to solving this problem, which attempted to avoid it entirely by having everything happen at once all over the place through magic. Between the misnomer and the heavy drain on the limited market for wizard labor, it's easy to see why the paradigm, though intriguing and not without useful lessons, failed to gain meaningful traction in the industry - perhaps ironically, there was just too much friction for it ever really to take off.
