I have taught of this seriously and I began to have a biased concern to bitcointalk if any signatures campaigns in bitcointalk can affects the existence of bitcointalk if they commit a crime that leads to government investigations.
First of all, I wish to commend you on this insightful question you just asked, and I will like to give you a brief example. You could all remember there was a signature campaign known as "ChipMixer", and months later we got to noticed it has been seized by the U.S government and under investigation. So did the investigation affect the forum? The answer is "NO", or did its investigation affect it's forum campaign participants? The answer is also "NO".
So in summary @ O.P, that answers your question that an investigation of a signature campaign can never affect the activities of the forum.
Secondly do we believe that bitcointalk can be obstructed by government if their is a noticeable crime by the management?
For me, I think that can only be possible only if the forum domain is under the host of a government regulated firm, but if the forum has an independent host, then that is likely not going to be possible..
But I stand to be corrected if I'm wrong on this.
From my understanding it seems to me that bitcoin existence is different from the bitcointalk forum and without the existence of bitcointalk forum bitcoin will continue existing, what's your take on this.
The forum was the official place for the discussion of the development of Bitcoin, so it has an important role to play in the continue use of Bitcoin
This idea came to me through what happened to the site of bitcointalk few days ago which I couldn't logins my account for sometimes, I wasn't happy when the incident occur
I thought I was the only one who noticed the domain "error" display few days ago when trying to login the forum, but never knew it was general, and as such that calls for concern, and I hope Sir Theymos needs to do something about it so that such doesn't occur anymore. Thanks