Are multi-vitamins dangerous?  

Being a pharmacist, I'd like to comment on this. It is not artificial. Better to use the word "extracted" than "artificial" because when you say "artificial" it means, not real. They are real. They are just extracted and preserved, extracted from either plant source or animal source.

You have a point there. But formulated vitamins have their own purpose and good use. Of course, they should not replace the intake of vitamin-rich foods, but take in consideration the modern lifestyle, the location and the availability of of vitamin-rich foods. Multi-vitamins were formulated to help people who do not have easy access to fruits and vegetables take in equivalent amount of vitamins. If you are living in a metropolis and you have a very busy or hectic schedule, that's when taking multi-vitamins is advisable. It should be taken as food supplement only.

Well i dont feel they are dangerous, i have been using for 16years now and feel great

There is a condition known as hypervitaminosis which I recently learnt about on mylot, it's scary but very rare. It's basicly an overdose, as with many things, excess is dangerous.
Yet too many people take them without consequence to consider it dangerous. If in doubt, ask your local pharmacologist to advise something, or just try things out yourself!
Something to apparently watch for is how quickly your urine changes colour when you take a supplement, as it implies how much of the vitamins are simply flushed out of the system straight away. =)