http://news.yahoo.com/flash-mobs-splash-mob-uk-man-arrested-planning-205428274.html

The problem here is that there is a fine line between thought crime, criminal conspiracy and actual criminal offense to incitement to commit crime, much of it is subjective and due to the nature of the language used i.e. semantics such as the infamous 'let him have it', which led to an innocent man being hung. One of the first tests should be if the actual criminal incitement charge actually led to any actual physical crimes being committed, which in all these cases did not.

Then there are the cases of police undercover agents also engaged in incitement to commit criminal offenses. These are never prosecuted especially when their aims are to publically discredit political activists groups, which the state deems objectionable.

Posting on an Internet site and computer crime also needs careful consideration due to nature of the publishing media simply because it can be so easily fraudulently used by the controlling authorities or unauthorised hacker.

I also get very nervous when I hear the term pre-emptive arrest.

http://www.guardian.co.uk/uk/2011/aug/01/police-arrest-97-notting-hill

I pretty sure that if the police come knocking down most folks door that they can make a good criminal case from anything that they deem to be an illegal substance. i.e. Esbit tabs equates to bomb making component material let alone chapati flour etc.