Wow, a LOT of random incorrect information in all these answers! Sorry, but it's true. Each answer is WAY off base!! There is so many rumours about garlic in oil, it's almost like TMZ's enetertainment "reporting" LOL!
Go here. Read the ENTIRE article.
The Canadian Food Inspection Agency & Health Services are superior in their information & food safety rules. They're awesome! It explains everything about the spore that releases a toxin (let's call it "spore poop")... the more spores, the more poop. Oxygen does NOT kill spores, it simply prevents them from multiplying. When you remove the air from the equation (you seal the garlic off from the air when you pour oil on it), you start the process if the spore is present. Because it's invisible, odorless, colourless and food with the spore & toxins do not look or smell spoiled or contaminated, there is just no way to know if it is safe -- why risk it?
You can do a garlic in oil, but you CANNOT leave it at room temperature, and you CANNOT keep it safely for more than one week in the fridge. After that point, even kept in the fridge, the toxins can be building up into dangerous levels. Because it's a toxin, it's not something we can build immunity to, like we do with salmonella.
The botulism toxin causes, among other things, paralysis, which is why they use it in those cosmetic procedures (BoTox which is the brand name, it was named such by the inventor of it,7, simply shortened "botulism toxin"). It paralyzes the facial muscles in the wrinkle-zones, so the face doesn't move to create wrinkles in the skin.
The original question was asking about dried garlic -- it is no different than regular fresh garlic. As soon as you seal it off from the air, the spores can multiply & grow. This is also why those vacuum sealers have big warnings not to use their system to preserve garlic. I doubt that dehydrated garlic or garlic salt or garlic powder/dust would have a good enough flavour for an infused oil, for starters. It would make the oil cloudy which would make it look yucky. It's just not worth the hassle to make things like that as gifts because who is going to trust it or be able to use it within a week of it's making? If you really really want to make something, make little herb planters for everyone! If you're on a tight budget, chives are great, they grow like mad from seed & are hard to kill. Or, just get a $2 lotto ticket for each person on your list -- it's safer and you might just get something good back from it. ;)
I hope all of this helps anyone who happens upon this page! :)