I've been hit square in the eye (lense) by several bugs, especially when riding at night. I've always had glasses of some sort on though. Being a contact lense wearer, they are basically a necessity in colder weather as my lenses will dry out in short order without something blocking the wind.
It may seem backwards to some, but I see plenty of utility in wearing glasses at all times while cycling but very little in wearing a helmet. I've never confirmed it but I've heard of eye protection being mandatory for motorcyclists in some states. If I get bored tonight I'll try to confirm it. Given the slow speed of most cycling, I would seriously object to any attempt at such a law for cyclists.