And they will be forced to learn, the hard way, that this is a bad way to approach algorithms design. The same argument applies to quicksort, and we know how that turned out: http://www.cs.dartmouth.edu/~doug/mdmspe.pdf
Yes, this approach may not work for a lot of situations, but there are some (as pointed out elsewhere in the comments), where it's perfectly reasonable, even desirable to improve the average runtime at the cost of the worst case.