What are the disadvantages of systematic observation?

If the the person who is being obsered know they are being observed they may act unsual and give off the wrong actions, speech, thoights and emotions as they may be nervous Takes a long time to...

its very time consuming

There is sometimes a great disadvantage in how easily focus can be broken and/or taken away due to even the most minute and perhaps unrelated occurrence when a person is blessed with overt...

Systematic observation includes naturalistic observation which is real life observation and structured observation which takes place in a natural environment but where manipulation is involved