I used to use socks, but have recently started opting for daybags. Socks prevent from UV and little nicks and scratches, but offer little protection from impacts. A 5mm daybag does a much better job. The downside of a daybag is it doesn't allow good ventilation and you'll find your board exactly like you put it in there 2 weeks ago....dripping wet.
if I am just going to surf and leaving aftwards I use a sock . If I plan on staying the day like I would in the summer I day bag it. If its a epoxy board you wanna use a day bag to protect for uv rays and heat in teh summer
For one a daybag does a great job of keeping sun off which helps the board form getting a "tan". The biggest thing is though it protects the thing from small inpacts, most people get lots of small "spiderwebbing" type cracks along their rail from impacts when not surfing. You can get good board bags cheap nowadays. Get the silver reflective kind if you can or a white one, to help with the sun. Plus just the getting the board to the beach and what not its nice to have some padding.
Dakine's daybags are awesome for like $45.00 way better than a sock, sock protects a board form the sun but wax sticks to those things really bad next thing ya know you have wax residue all over your board from a sock. SPend the extra $20 on a daybag its worth it.
there used to be someone in monmouth country area (i want to say neptune to be specific) who made custom board socks. i have seen the add on craigslist, i think as recently as last summer the ad was up. does anyone know how i might get in touch? they were like $25 and you could get them mde custom to the size of your board.