What are the risks of using ecstasy?

Here is a real answer that people will actually understand. The risks of using ecstasy are permanent retardation, heart attack, stroke, seizures, coma, and death. The reason many people use ecstasy while knowing all of the risks is because for many people, there is no consequence. It is truly a game of fate, or a dance with death.

"While the short term side effects and contraindications of MDMA are fairly well known, there is significant debate within the scientific and medical community over the long term effects and the possibility for physical harm arising from MDMA use.

- Government studies
The chief executive of the UK Medical Research Council stated MDMA was "on the bottom of the scale of harm," and the Science & Technology rated it of lower concern than for alcohol, tobacco, and cannabis, when examining the harmfulness of any given drug. The UK study placed great weight on the risk for acute physical harm, the propensity for physical and psychological dependency on the drug, and the negative familial and societal impacts of the drug. On these factors, the study places MDMA relatively low, which reflects its lower score in comparison to the risks of alcohol.

- Physical
The short-term health risks of taking MDMA include hypertension, dehydration and hyperthermia. In the raving subculture, use of MDMA can increase the risks of dehydration and hyperthermia, as the drug's stimulatory effects can mask the body's normal sense of exhaustion and thirst. The risk of hyperthermia may be increased by a high fat diet, but more importantly MDMA is implicated in affecting the mechanism of uncoupling protein (UCP), more specifically UCP3 in mitochondria.

MDMA affects the regulation of the body's internal systems. Continuous dancing without sufficient breaks or drinks can lead to dangerous overheating and dehydration, and serves to significantly enhance the drug's neurotoxic action. Drinking too much water without adequate salt can cause hyponatremia or water intoxication, although this is less common than overheating.

Hypertension is a risk in some users due to the increase in heart rate and blood pressure. This risk increases as dose increases which can lead to overstimulation of the heart and ultimately death.

- Neurological overview
It has been established that MDMA affects the brains of humans and lower primates differently, especially in terms of long-term changes. In both animals, MDMA causes a reduction in the concentration of serotonin transporters (SERTs) in the brain. Baboons who were given a neurotoxic dose of MDMA only showed partial regrowth of SERTs when scanned a year later. In contrast, human studies differ in that those who had never used ecstasy were indistinguishable in PET brain scan studies from former ecstasy users. However, the same study also concluded that the reduction in memory performance due to heavy, prolonged MDMA use may be long-lasting.

Although oxidative stress (see neurotoxicity theory below) may cause SERTs to degrade faster than they are able to be replaced, the serotonin axon itself seems to have been spared, which indicates that neurotoxicity may not be the means by which SERT count was reduced. It is possible that excess serotonin in the synapse due to MDMA, especially if uses occur within a short period, causes the serotonin cells to produce fewer SERTs, a phenomenon which has already been demonstrated with other serotonin-depleting drugs. MDMA use may also cause a decrease in the number of serotonin receptors on the dendrite of the neuron. (See down-regulation theory below.)

For a detailed and comprehensive explanation of this topic, see TheDea.org's evaluation of studies."
Source and further information:
http://en.wikipedia.org/wiki/Methylenedioxymethamphetamine#Health_concerns

the main risk is feeling too dehydrated, possibly from dancing around on a high and them overcompensating by drinking loads of water and effectively drowing your brain.
get a responsible friend to keep an eye on you and if you feel thirsty, drink S-L-O-W-L-Y

inappropriate and/or unintended emotional bonding
tendency to say things you might feel uncomfortable about later
mild to extreme jaw clenching (trisma), tongue and cheek chewing, and teeth grinding (bruxia)
difficulty concentrating & problems with activities requiring linear focus
short-term memory scramble or loss & confusion
muscle tension
erectile disfunction and difficulty reaching orgasm
increase in body temperature, hyperthermia, dehydration (drink water)
hyponatremia (don't drink too much water)
nausea and vomiting
headaches, dizziness, loss of balance, and vertigo
sadness on coming down, sense of loss or immediate nostalgia
post-trip Crash - unpleasantly harsh comedown from the peak effect
hangover the next day, lasting days to weeks
mild depression and fatigue for up to a week
severe depression and/or fatigue (uncommon)
possible strong urge to repeat the experience, though not physically addictive
possible psychological crisis requiring hospitalization (psychotic episodes, severe panic attacks, etc) (rare)
possible liver toxicity (rare)
possible neurotoxicity (controversial)
small risk of death. Approximately 2 per 100,000 users have extreme negative reactions resulting in death. (rare)

One-way trip to Pluto.
Jimmy Hendrix and Jim Morrison will be there waiting for arrival.

My 2 cents.

Risks caused by long-term use are:
- Dehydration
- Hypertension
- Hyperthermia
- Heart failure
- Kidney failure

http://www.teendrugabuse.us/ecstacy.html

Other than the obvious already stated death!

sex, fun, brain damage, death, and fun.