my theory

Cross Trades:

5/5/2009 = 3,250,000 at $1
5/5/2009 = 2,000,000 at $1
5/5/2009 = 1,894,785 at $1

6/5/2009 = 3,250,000 at 96 cents

We know that none of those cross trades triggered a substantial holder notice, so there must have been a minimum of two recipients.

If they bought on the presumption that UMC was soon to be taken over, they might now feel that this is unlikely to occur given the recent proposed BHP/Rio JV, thus the aggressive selling today.

I was concerned about the fact that those cross trades went to multiple parties since I thought they were after a quick buck. I believe that justification of my concerns are being played out today.