It is used by rock guitarists way too often by stringing different power chords together to form a riff. This goes against western diatonic music theory which says you should not have parallel 5ths or octaves, let alone both of them simultaneously. Despite this fallacy, rock guitarists have chicks and money while classical musicians have neither. Go figure.
Yeah. He mustn't use power chords.
G5 with the octave
For the person who said that parallel 5ths and 8ths shouldn't be even used, I think you'll find this is only relevant to Baroque and Classical music. What about Debussy and his use of 5ths and 8ths? In the right context, it can sound fine.
So please, stop living in the 18th century.