In the Bill Nye versus young earth creationist Ken Ham debate, Ken gives this response to radiometric dating:
Unfortunately, Bill Nye did not have a satisfactory response to this. Is there one? Yep. Notice from the above video it is apparent that a creationist took the samples and then sent them off to the laboratory for dating (Potassium-Argon for the basalt and radiocarbon for the wood). There is a method of radiometric dating called isochron dating that has a built-in check for most forms of contamination. However, Chris Stassen of TalkOrigins notes that
some dating methods (e.g., K-Ar and carbon-14) do not have a built-in check for contamination, and if there has been contamination these methods will produce a meaningless age. For this reason, the results of such dating methods are not treated with as much confidence.
Bingo: a creationist sent in some stuff for dating when the dating method in question had no built-in check for contamination! Potassium-Argon and radiocarbon dating is not necessarily useless, but one does have to be careful about not sending in contaminated samples, and I am willing to bet the creationists who took the samples did not do that.