"This incident had the potential to turn into a practical joke leading to a fatality", Mr Rowan added.

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Second, please stop comparing Twitter to Zynga (which is a game publisher) and Groupon (which is an accounting practical joke).

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In some countries, bamboozled bargain-hunters, abandoned in an obscure field as part of a giant practical joke, would probably turn furiously on their tormentors.

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"It's a big, busy library and someone has played a practical joke - it's gone unnoticed for a while and once staff noticed they changed it, " he said.

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The real question facing industrialised countries is how to create a legal environment that counts cyberaggression not as a kind of practical joke, but a grave breach of the legal order, akin to terrorism, international organised crime, or aggression against another state.

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