In theory Silicon Valley could have a dramatic effect on journalism in the modern world. The reason for this could be the fact that companies like Google and Facebook are both digital journalism outlet, so they could have influence on what would be posted. Social media devices like Facebook can also control what the general public post which could be seen as news, like live action video, normal videos or images.
It could be argued though that Silicon Valley doesn’t have an effect on journalism. This is because not every media outlet is based in Silicon Valley. Also in the UK we have the BBC and various newspapers that are based in the UK so probably would not be affected by Silicon Valley.
In general I don’t think there is enough evidence to support the idea that Silicon Valley has a major influence on journalism and if it does it would be incredible minor.