Botulism threat is incredibly low
I know this link is very old, but it comes up pretty high in the google search, so I figured I'd update.
There seems to be a lot of cautioning about storing garlic in olive oil, but I have to say that the risk is incredibly low, like struck by lightning while spelunking low.
See the Center for Disease Control website discussion of Botulism:
It doesn't let me post urls yet, so search the CDC website for botulism.
Below I have pasted a pertinent paragraph. First though, the stats. There are about 145 cases of botulism, of which 15%, or 22 are foodborne. If you look at the paragraph below, particularly what is bolded, you can see that there have probably been about 3 cases from garlic in oil ever. And there is a 3-5% death rate for botulism cases in the US.
I'm not saying to not be careful, but you really have to look at the facts before becoming concerned and raising alarm. You would probably reduce your risk of illness more by taking a shower and soaking in sanitizer every time you go to the bathroom than you would by not eating garlic stored in oil. Or for a more realistic comparison, you could probably reduce your risk of injury by taking one fewer trip to the store in a car each year. >40,000 people killed by cars every year and many many more injured. I don't want to seem like I'm attacking anyone here, but just want to put things in perspective.
Botulism can be prevented. Foodborne botulism has often been from home-canned foods with low acid content, such as asparagus, green beans, beets and corn. However, outbreaks of botulism from more unusual sources such as chopped garlic in oil, chile peppers, tomatoes, carrot juice, improperly handled baked potatoes wrapped in aluminum foil, and home-canned or fermented fish. Persons who do home canning should follow strict hygienic procedures to reduce contamination of foods. Oils infused with garlic or herbs should be refrigerated. Potatoes which have been baked while wrapped in aluminum foil should be kept hot until served or refrigerated. Because the botulism toxin is destroyed by high temperatures, persons who eat home-canned foods should consider boiling the food for 10 minutes before eating it to ensure safety. Instructions on safe home canning can be obtained from county extension services or from the US Department of Agriculture. Because honey can contain spores of Clostridium botulinum and this has been a source of infection for infants, children less than 12 months old should not be fed honey. Honey is safe for persons 1 year of age and older. Wound botulism can be prevented by promptly seeking medical care for infected wounds and by not using injectable street drugs.