Yeah, I don't know if I would say or do anything, unless you feel like it is a safety concern. Is he running into things or falling down and tripping over stuff? Then I might mention it. I don't think I would put elastics into his hair, unless I took them out before mom and dad got there!
I used to have a little girl with the same issue. I did put her hair into a clip or ponytail, but only because she was extremely pigeon-toed and kind of clumsy. She had a hard enough time as it was with walking, nevermind having hair in her face!
I would definitely be tucking it up under a cap or hat while outside, though.