damnek is right, I've seen it happen.
If you watch the orderbook on Bitstamp you can see when someone places a limit bit above/below what the market is asking. Sometimes this makes it's way through to the API and shows up on the chart.
It happened with $150 as well even tho it never hit.
Surely this is a serious problem then?
It opens the possibility of gaming the market by inserting non-existent trades into the charts and skewing the data.