Chances are it won't keep you out of the US in the future.

But... any appeals process that the Customs Service has is pretty cumbersome. They double-billed me duty on some artwork (that was shipped in two boxes) that I brought back from the UK one time. It took a couple of months to get it resolved, but I eventually got the improperly charged money back. I did copy my elected representative on the correspondance.

As for any future entries into the US, I sat on one international flight next to a gentleman who ended up with a black mark in his Immigration record after getting caught bringing Cuban cigars into the US from Europe. The computer flag caused him to be sent for secondary on every entry to the US from then on. The flight we were on was his 20th since the incident, and it was the 20th time he was sent to secondary.