I agree with Rid on this one. There are numerous complications that can occur with an IV and if you're looking to make EMS your career and continue on to paramedic, you might want to re-consider practicing a skill that is beyond your scope of practice.
I also agree that very few paramedics realize what can go wrong with an IV as well. Of course, there is infiltration, but there is also the idea of opening up a very nice port of entry for any bad, nasty bug that will fit. There is phlebitis, catheter shearing, scaring, bleeding, and even people that have accidentally hit arteries instead of veins.
No procedure is without its risks and it's important for an educated provider to be able to weigh those risks for the benefit of the patient.