As you know, I have little trust or faith in the food industry and on this site I put example after example of How the Food Industry Endangers Your Health Daily. The problem is that they can make money - lots and lots of money - by putting your health at risk.
Most health-conscious people are, to one extent or the other, aware of this fact and try as best they can to "live naturally" by avoiding processed foods. They try to eat whole foods instead and very often try to use herbal and other (seemingly more) natural supplements in order to improve and maintain their health. By the same token, I find many guys that write into me have an inherent trust in supplements to improve their testosterone, erectile function and health in general and an inherent distrust of drugs and the pharmaceutical industry.
This often wholesale acceptance of supplement is potentially very dangerous. The reason? Greed.
The same motivator that has corrupted the food and pharmaceutical industries is little better in the supplement industry. Again, people can make money - and a lot of it - by selling you something that will hurt your health. I have already covered How Many Everyday Supplements and Vitamins Can Be Dangerous. Imagine how dangerous some of the more exotic supplements that guys take for men's health or bodybuilding are! It's not pretty.
The Men's Journal recently did an excellent article on testosterone-related examples of this fact.  They gave many examples, but one of the most prominent was a "muscle activator" by Tren_Extreme. One innocent buyer took this product for several months and found that he itched, couldn't sleep and lost 34 pounds inexplicably. These are all classic signs of liver damage and the FDA discovered that the manufacturers had been adding a powerful untested synthetic steroid.
As I cover in my link on Bioidentical Testosterone, steroids often have side effects and this one was no exception. The individual involved was still struggling to recover from the damage that was done. Why would Tren-Extreme put its purchaers at risk with an untested steroid? Greed.
Guys have also gotten themselves in trouble with erectile dysfunction products as well. One poor guy took an erection-related supplement which produced a "super erection" from the Yohimbine ingredient.  Of course, priapism, an erection that last over about four hours, will injure penile tissue and can cause permanent damage. The doctors actually had to operate on this individual and apply a shunt.
NOTE: Be very careful with yohimbe. One 37 year old bodybuilder overingested it before a competition and lost consciousness, went into seizures and had about twice normal blood pressure levels. 
There was a drink supplement called Total Body Formula or Total Body Mega Formula that the FDA recalled in 2008 poisoned consumers with overdoses of chromium and selenium, leading to deformed nails, hair loss, diarrhea and a host of other nasty symptoms.  Again, this list could go on and on, but you are far more safe avoiding all such products all together unless it is from a manufactuer with a stellar, long term track record.
It's simply not worth the risk. Most of you can achieve incredible health results with just food and exercise alone. You can Heal Your Erections with Food, Improve Your Testosterone Naturally and put on muscle without any additional chemical regardless of age.
You only get one life - don't put it in the hands of some greedy fool that just wants to fatten his bank account...
1) Men's Journal, Nov. 2009, p. 63.
2) Journal of Medical Toxicology, "Refractory Priapism Associated with Ingestion of Yohimbe Extract"
3) Clinical Toxicology, Sep 2009, 47(8):827-829, "Acute neurotoxicity after yohimbine ingestion by a body builder"
4) http://www.fda.gov/Safety/MedWatch/SafetyInformation/ SafetyAlertsforHumanMedicalProducts/ucm070027.htm