DonJean-

you asked:
"Why is someone shorting?"

Manuel Asensio is a professional short interest player.
His short position on AOB developed in early Summer, 2009, after it was apparent that AOB would disappoint
in comparative earnings, and also after AOB management disappointed investors with a real estate deal which apparently was a sweetheart deal, arranged by senior management.

Here is AOB, as presented by Asensio:
http://www.asensio.com/SearchResults2.as...

As you can see from the link, China Sky Medical (CSKI) is also in Mr. Asensio's gunsites....

Now- here are the relative performances of CSKI and AOB in a daily candle chart for 2009.
Note the late Summer/early Fall PPS deterioration, especially for AOB:
http://stockcharts.com/h-sc/ui?s=AOB&p=D...

Mr. Asensio has been on the correct side of the trade from his short position, taken in late Summer, 2009.
He will need to cover into the close of the year. Tax loss selling season is coming to an end,
and the upcoming conference calls- for Q3'09 in a week or so, and for FY 2009 in February, 2010- should positively forecast earnings into 2010. Hopefully, AOB will aso explain in the Q3'09 CC what new capital from the recently authorized 150MM USD stock offering may be used for.

Manny Asensio would be the last person to explain this, but the right side of the trade going forward- if your time horizon goes to mid-2010
or late 2010- is long AOB from around $4.00 and a couple of cents...
JMO.
-r.

PS- Manuel Asensio is a Harvard MBA. He is very aggressive in his investment style, and again, he is a short player- probably the best-known short interest player in the biotech field. I recall his short positions on SVA and other avian flu plays in 2005-2006.
Manny was actually on the wrong side of the trade regarding avian flu, so he is hardly infallible. He has also been on the losing side
of several civil cases, a point his website may have inadvertently overlooked, since no mention is made of them...