This is a very interesting case, indeed. Thus, I'll split my post into two parts: One regarding this individual agreement on its own, and the other based on a broader view of things.

Part one:
Unless there is any objection to the log that was posted, it seems pretty clear that the original agreement should be considered void. Fjordbit has a good point, however, in that the silence portion should have its own value. Thus I would like to see one of the two following outcomes:
1) EskimoBob refunds 5.3 BTC and the shares are returned to him. No, he will not need to pay the original escrow fee. The reason he should not have to pay the escrow fee is because usagi agreed to pay the fee himself, instead of asking EskimoBob to split the fee with him or at least including the escrow fee as a penalty should the agreement be broken. Additionally, the escrow failed to follow the agreement all the way through by releasing the funds immediately instead of waiting an agreed upon amount of time to ensure that the agreement was kept by BOTH parties. This is besides the fact that it is not legal to indefinitely buy someone's silence. However, I think that we can all agree that EskimoBob did not stay silent long enough to be considered reasonable by anyone's standards.
2) EskimoBob refunds the difference between the market value of those shares at the time of the agreement and the value he sold them to usagi for (.53 BTC/share) and usagi provides nothing in return (other than the satisfaction that the agreement was successfully unwound). It's safe to assume that this difference was the agreed upon value of silence for EskimoBob.

Part two:
Here's where things get interesting. It is board policy that, in order to help scammer investigations, NDA's and other such agreements will not be honored for the purpose of the scammer tag when the agreements are broken in order to reveal a scam. Interestingly enough, this seems like it might be the case. I will absolutely need to do more reading into this. If anybody can help shed some light on the issue of usagi allegedly investing BMF funds into non-mining operations, I would appreciate that.

There's also the matter of where the funds used to pay EskimoBob came from. Did they come from a business that was in default? If so, that automatically makes usagi a scammer, placing EskimoBob off the hook.

For these reasons, it will most likely take a few weeks to decide this case. If EskimoBob wants to make it easy on me, he can simply do one of the two options I laid out in part one. As always, the scammer tag decision does not have anything to do with the actual legal system, so keep that in mind when deciding what to do.