Many people have been running alot of heroics since the start of cata, and have been capped on justice points even after buying all the upgrades they need. You can turn your excess points into small amounts of gold...wont make you rich but better than letting the points rot. This might be common sense for some, but useful for others .
Besides the obvious option for enchanters (buying the 950 point items and d/e'ing), non-chanters can buy Windslicer (page 5 of the vendor, top right item) which only costs 950 justice points, but vendors for 26g2s66c. All you need to do is wait for the refund period to wear off, and then you can sell to a vendor. Instead of being capped, you can make 100g . As i said, wont make you rich, but better than just leaving the points there doing nothing.