After all these years of dropping my bike off at the LBS I started doing my own work for no reason other then I enjoy it and tonight I noticed what you see in the picture below.
These holes are at the ends of the forks, seat stays, chain stays and even the top tube.
Sure it's a cheap GT Hybrid that's 10 years old but I like it for a beater. I live by the ocean and I'm pretty sure it can't be good to have a bike that's like swiss cheese. You can even see the rust that's developing.
Is there any functional reason for having holes in a frame (on the inside of the tubes mind you)?