I haven't read Bajakajain in detail, but out of curiosity I checked out Kennedy's dissent. There seems to be a fundamental disagreement between the judges in this case about just how culpable the defendant really was, and it colors both rulings. I haven't read too carefully, but Kennedy seems to suggest that the only kind of fine he would deem excessive would be a fine the defendant would be totally unable to pay.

There also seems to be a technical dispute about when to apply the 8th amendment. Kennedy writes:

So-called remedial penalties, most in rem forfeitures, and perhaps civil fines may not be subject to scrutiny at all.

It seems this case provides an opportunity to examine these questions more carefully. I'm all for it.

(As an aside, I think in rem forfeitures violate the due process clause but thats a whole other ball of wax.)