obviously it depends upon what level you choose to compete at as to how carefull you are with respect to supplements.
Howevere if you ever choose to go to a competition that you can be drug tested at: 1 in britain and wendy will have been tested after it
then supplement taking is up there with risking judging your alcohol intake against a breathalyser! so just not worth the risk.
not long ago there were some supplements out there with the australian institute of sport label on them and this was taken to mean that they were "safe" with respect to testing...... it was not
As it stands the laws are not set up to victimize supplement manufacturers but untill they bring there production values in to line then they can not be ratified by any institute of sport or wada. The major issue outside of straight ingredients is the manufacturing process which may well use equipment that has been used to produce another product (in some cases steroids etc) this is not allowed under pharmaceutical regulations.
So sadly it has to be an attitude of avoidance of these products, the risk is just too great.