Is that accurate? Was the problem not resolved with the May 5 update, or is it a different issue?
I'm not an economist, but it indicates a high demand for bitUSD, possibly due to the recent rise in BTS price. Also, a lot of users believe that the market rules aren't balanced to provide enough incentive to shorts.
Check out the discussions regarding the BitAssets 2.0 proposal, an evolved form of BitAsset mechanics that will provide much better liquidity.
BitAssets 2.0: https://bitsharestalk.org/index.php/topic,16127.0.html
Response to design critiques thread: https://bitsharestalk.org/index.php/topic,16143.0.html