EFF accepts donations in Bitcoin, so their lawyers must have decided that it's not clearly illegal or bad PR.
I'm not sure that follows. What's more, if people generally use that reasoning, and EFF is wrong (or lacked due diligence in such an estimation), then people will now be able to cite both SIAI's and EFF's actions when using such reasoning.
And then you have an information cascade, where everyone believes Bitcoin "must be okay", all based on an expert judgment that never existed.
Have any other cryptography experts published critiques of Bitcoin? I'd contribute to a fund to get Bruce Schneier to spend more time on this.
There is very little more to being legal than an information cascade.
Now you can donate to Singularity Institute using Bitcoin.
Currently Bitcoin mining appears to be profitable as only bubble economics can be. Already some Less Wrong users have purchased GPUs and started mining Bitcoin. Please consider sending some Bitcoins to SI at address 1HUrNJfVFwQkbuMXwiPxSQcpyr3ktn1wc9
2014 Edit: Please donate Bitcoin by using the Bitpay link on MIRI's donate page. Thanks!