I have a 5-month-old infant. It's always many hours after feeding - he is burped. He has always done it, but not every day and mostly just a little. Sometimes, it's a lot of volume. Is he losing nutrition or there not much actual milk coming out?
A book I read (perhaps one of the What to Expect series) noted that a little bit of spit-up forms a puddle that looks like a lot. To demonstrate this to yourself, take a tablespoon (~15 ml) of milk (not breast milk) and pour it on your counter. Is your infant spitting up that much? More? Less? Rarely do my kids spit up that much. And that is far less than a feeding. Obviously, I don't know how much your kid is spitting up.
My baby girl regurgitated at least once a day until she was several months old, sometimes "The exorcist" way (http://45.media.tumblr.com/tumblr_lb5tqhFGmg1qb9nsso1_500.gif). We were worried as you seem to be, and reassured by our doctor, advising to "test" it the same way Ze'ev Felsen suggests, by pouring a table spoon of water on the floor to have a reference. I did, and indeed although the quantity on the floor looks big, it was only a table spoon...
My advise would then be to just keep a close eye on your baby's weight curve, this being a very good indicator of feeding quality.
Although probably not a problem if this is the only symptom, seemingly random spit ups like this are a common sign of a mild intolerance to something the mother is eating. Acidic foods are a common culprit. When this happens take a note of what was eaten earlier, and a pattern may be found.