You can't just believe one person's "word" about propecia or any other drug. Look at this:
The 2005 Prostate Cancer Prevention Trial (PCPT) showed at a dosage of 5 mg per day, as is commonly prescribed for BPH, though much higher than the 1 mg generally prescribed for hair loss, participants taking finasteride were 25% less likely to have developed prostate cancer at the end of the trial compared to those taking a placebo.[1] It appeared (incorrectly) that finasteride increased the specificity and selectivity of prostate cancer detection, thus, a seemly increased rate of high Gleason grade tumor. A 2008 update of this study found that finasteride reduces the incidence of prostate cancer by 30%. In the original study it turns out that the smaller prostate caused by finasteride means that a doctor is more likely to hit upon cancer nests and more likely to find aggressive-looking cells. Most of the men in the study who had cancer — aggressive or not — chose to be treated and many had their prostates removed. A pathologist then carefully examined each of those 500 prostates and compared the kinds of cancers found at surgery to those initially diagnosed at biopsy. Finasteride did not increase the risk of high-grade prostate cancer.[2][3]
In order to make a proper evaluation of the risks involved you must look at several studies, look at the details of what the "300%" study found, and then make a proper evaluation.
The effects of the drug:
In a 5-year study of men with mild to moderate hair loss, 48% of those treated with Propecia (finasteride 1 mg) experienced some regrowth of hair, and a further 42% had no further loss. Average hair count in the treatment group remained above baseline, and showed an increasing difference from hair count in the placebo group, for all five years of the study.[4] Propecia is effective only for as long as it is taken; the hair gained or maintained is lost within 6–12 months of ceasing therapy.[5] In clinical studies, Propecia, like minoxidil, was shown to work on both the crown area and the hairline,[6] but is most successful in the crown area.
It seems that it at least halts hair loss in 90% of users not suffering from brutal brutal hair loss.
It seems like there have been rapports about erectile dysfunction and other side effects. The studies show that 1-2% of uers get some side effect and forthe brutal majority of these, the sides go away.
For the very small amount of people that get persistent problems after quitting the drug, it can be looked upon as an inherit risks found with any drug. Practically any drug has the potential to give one person or another brutal side effects like anaphalytic shock. If anything, the amount of users getting these effects seems to be incredibly small.
An example: Many people are popping the drug Modafinil to stay awake and reduce fatigue, yet most of them are not aware that a small number of users have gotten severe cutaneous adverse reactions from the drug.
From the majority of the data that can be found, it does not seem like these horror stories about the drug is something that should be used as the main guidance when choosing to use the drug or not. One must look at the totality of all research, and find out what the was done during the 1999 study and what the follow up reactions were, including eventual follow up studies.