Physical Danger
Your hand-blown glass animals and jewels are a huge hit on Etsy. However, any time you have to work with material that's essentially molten lava, there's bound to be an increased chance of...say, death, or at the very least burns, disfigurement, and respiratory lung disease from inhaling chemicals (source).
You sure you wouldn't rather knit a few nice sweaters instead? (Watch those knitting needles, though: They can be pretty pokey.) Maybe you'd like to make pretty decoupage boxes? (Scissors and razor blades are sharp.) Perhaps some nice pottery (toxic glazes, silica dust in the air, blazing hot kilns), or embroidery (needles, eye strain), or wood carving (chisels, dowels, and other sharp implements that can cut and stab), or...
Okay, you get it. Crafting is a dangerous, dangerous business, no matter what you get into.
Even the most innocuous of crafts, like scrapbooking, can give you wicked paper cuts. And since a lot of crafts involve sitting still for long periods of time, you always run the risk of your legs falling asleep, your back hurting, and your eyes getting strained.
It's dangerous to go alone. Take a good office chair and the appropriate safety gear, be it safety goggles or thick gloves, with you.