It's vulnerable in that whichever threshold N that you choose allows for N participants to conspire to publish ahead of time, or M - N to conspire not to publish after the fact.
interesting. i hadn't seen this although I implemented something effectively the same, except that all keys (which could be any number ≥ 2) be combined to reveal the secret (or any information about it).
http://www.moserware.com/2011/11/life-death-and-splitting-se...
It's vulnerable in that whichever threshold N that you choose allows for N participants to conspire to publish ahead of time, or M - N to conspire not to publish after the fact.