Yes, GMOs (genetically modified organisms) are unsafe for your health and here is why.
1. GMOs is linked to the growing spread of autism (studies in rats have indicated that this is most likely true. soruce: http://throughtheeyesofautism.wordpress.com/2009/09/29/autism-and-genetically-modified-foods/)
2. GMOs reduce the resource diversity of crops and produce worldwide. This is especially dangerous because the lack of diversity in our food source is not well prepared to fluxuate with the increasingly unpredictable climate change. Diversity is essential for global food security.
3. GMO pollution. Once GMOs become inbred with natural or organic organisms you cannot reverse the process. As the winds, water, insect, animals and soil carry GMO particles to other farms it contaminates and cross breeds with those varieties thus bastardizing all of our food.
4. GMOs over multiple generations increase infertility and sterilization in those who eat it. (Some have suggested that GMOs are actually a tool to curb over population on the planet).
Did you know that studies done when rats were fed with GMO soy most of the rats lost the ability to have babies in three generations? Less than 15% of the rats who wear able to produce offspring produces very small sickly babies. If humans react similar to GMO tainted food, we are currently inbetween the 1st and 2nd generations.
Here is another scary thing: Approximately 75% of all food products in an average United States grocery store has some kind of GMO in them. Mostly in the soybean oil, cottonseed oil and other vegetable oils. (Source is the 2/9/12 radio broadcast on Coast to Coast AM http://www.coasttocoastam.com/show/2012/02/09)
Monsanto, Kraft and other large corporations who make large profits from GMO based foods have run massive campaigns to spread disinformation about the safety and/or necessity of GMOs. Here are some links about Monsanto and disinformation:
Monsanto's Round-Up is proven to cause major medical problems in those exposed to it.
Round Up the cause of birth defects
Are GMO (genetically modified organisms) bad for me?
basic overview of GMOs: http://www.csa.com/discoveryguides/gmfood/overview.php
Seeds of Deception by Jeffrey Smith.