What am I supposed to believe?!!!!
taken from:
www.stiller.com/water.htm

Microwave to Heat Water Hoax
Like many 'danger warning' type hoaxes, this contains some elements of truth but still should not be forwarded. (Remember, just because a warning contains an element of truth does not mean it should be forwarded. Would you circulate a warning that says to lock your doors, otherwise a burglar may enter?)

Here's the most common version of this warning:

THIS IS A VERY COMMON PRACTICE AT MOST OF OUR HOMES

Microwaving Water to Heat it Up

I feel that the following is information that any
one who uses a microwave oven to heat water should be
made aware of. About five days ago my 26-year old son
decided to have a cup of instant coffee. He took a cup
of water and put it in the microwave to heat it up
(something that he had done numerous times before). I
am not sure how long he set the timer for but he told
me he wanted to bring the water to a boil. When the
timer shut the oven off, he removed the cup from the
oven. As he looked into the cup he noted that the
water was not boiling but instantly the water in the
cup "blew up" into his face. The cup remained intact
until he threw it out of his hand but all the water
had flew out into his face due to the buildup of
energy. His whole face is blistered and he has 1st and
2nd degree burns to his face which may leave scarring.
He also may have lost partial sight in his left eye.
While at the hospital, the doctor who was attending to
him stated that this a fairly common occurrence and
water (alone) should never be heated in a microwave
oven. If water is heated in this manner, something
should be placed in the cup to diffuse the energy such
as a wooden stir stick, tea bag, etc. It is however a
much safer choice to boil the water in a tea kettle.
Please pass this information on to friends and family


What is described above can almost happen. It is possible to super heat water in a microwave (this is also possible but less likely on a conventional stove). A disturbance can then cause the water to "explosively" boil (not really blow up though).

Hopefully the language to 'Please pass this information on to friends and family' is a sure-fire sign to you that this should not be forwarded.

The incident above is fictional and please never forward any such warning that asks to be forwarded or passed to others but do take care when heating water (whether it's in a microwave or by any other means). It is quite possible to have water heated to the boiling point and then trigger a release of steam similar to that described in the above story. (It is easier to heat water uniformly in a microwave than on a stove top so this is more somewhat likely to happen with microwave.) Adding instant coffee for example, can cause the heated water to bubble up. The FDA has a warning on the risk of burns from overheated water. People have been hurt after heating water in a microwave when it suddenly bubbles up so please do be careful but please do not forward this hoax.

There are a number of similar warning hoaxes to this one. Some warn about totally absurd threats and others warn about things that really could happen. Simply because something could happen, please do not circulate the warning hoaxes. If you really feel you need to forward one of these warnings, please remove the text that says to pass it on to others (otherwise these 'warnings' will never stop circulating.)