Fortunately though, this is the last one. That should clear the way afterwards for an upward direction.
The announcement of the first USMS SR auction (2014-06-27; won by Tim Draper) apparently caused a drop in the price on 2015-06-11, from ~650 to ~590, that was reversed on 2014-06-30 when the result was revealed.
The second auction (2014-12-04; won by a SecondMarket syndicate and a small bid by Tim Draper) had no discernible effect on price, that remained pretty stable at ~375 for about a week before and a week after it.
Abut a week before before the third auction (2015-03-05; won by itBit), the price rose from ~240 to ~280, but probably for other causes. It remained stable through the auction, and had another small rise a few days later.
So it would seem that, after the first one, the market got used to the USMS auctions and ignores them (or "prices them in" well in advance).
This is the last USMS SR auction, but two more have been announced: the auction of ~24'500 BTC by the Australian government, and the auction or return of ~200'000 BTC by the MtGOX trustee, maybe by the end of the year.
Jorge: Actually, I tend to like to bash you for providing crappy information...
The above post is an exception, and I find it a very informative summary of the auction situation. Thanks for that contribution.