Deprived already made most of the points I wanted to make. But let me add;  I would avoid betting on the short term, this market isnt always very rational or quick to understand, and low liquidity could hurt us. More importantly, right now, I would be wary of shorting (or buying) mining bonds or shares in general. The asic switch is difficult to predict, we dont know how many devices will be shipped, when they will be shipped, who will get them first and how long it will take for the others to receive them. Its even more difficult to predict how investors will react on what I expect will be a brief but very substantial gain in dividends (especially for those who get them early), to be followed by very sharp and prolonged decline towards nothingness. Most likely this will create great shorting opportunities at some point, but I wouldnt start the bet today, I would rather wait until these companies are mining with asics and see if enough investors get fooled by the apparent spectacular rise in perceived profitability and/or dividend payments.

One last thing, not directed to you in particular, but the fact the vast majority of assets on GLBSE are IMO not worth buying, shouldnt be viewed as criticism on all the issuers. Its not (always) their fault if investors will buy the "least worst" at whatever the current price,  or hang on to shares that are ridiculously overpriced.