Can I set up only utm_source?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Tim Capper: Yup Thats Fine:
  https://ga-dev-tools.appspot.com/campaign-url-builder/
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  Jay Lo: Thank you so much, But I just found where did I saw it, it`s actually Google`s offical guide, it say :
  
  When you add parameters to a URL, you should always use utm_source, utm_medium, and utm_campaign.…Lihat Lainnya
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  David Kutcher: You CAN only use source, but it will screw up many of your default reports which are built on the junction of source+medium (for example for channels)
  
  You can also just use source+medium and leave off campaign if you`d like, as you might not need that campaign data but just want to make sure that the traffic from a link is showing in the correct source/medium.
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  Jay Lo: David Kutcher I see, so it will still works but mess up with the data, thank you so much!!
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  Dave Elliott: Would say you should probably use more cause it`s useful but it`s fine to just use source
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  Benj Arriola: utm_source : if it is GMB, sure make it whatever. Or you can just keep it as Google since it is google anyway, but if you want to segment out traffic from google maps, then probably just add GMB in utm_campaign instead.
  
  utm_medium : I have 2 suggestions here. If it is a plain submission on GMB, then keep the medium organic. So it does not mess up the default channel, if you make something custom, it may end up in the channel named (Other). And since the user experience of something finding something on the maps, it is often coming from a search result anyway. Now if this is a paid ad that appears in map results, then this is no longer organic, I would use cpc instead for the medium.
  
  utm_campaign : this is where I will add in the GMB, you can just filter organic results or filter google traffic by campaign in a custom segment of you want to see GMB traffic alone, or traffic excluding it. Just thinking out loud... I might do utm_campaign=local-gmb
  
  That way in the future if ever I do submissions to Yelp, Citysearch, Nextdoor, EYP, or any other local portal, I can filter by campaign contains local if I want to see the performance of all local directories together. But I can still filter by GMB also if I want to see GMB numbers only.
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  David Kutcher: No no no!
  
  Geez.
  
  If GMB, keep source: google, medium: organic, campaign: GMB
  
  Otherwise links from GMB listings, which are from organic Google search, won`t show correctly as being from the correct source and medium.
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  Benj Arriola: I thought that was what I said, but said it in a complicated way. 😀
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  David Kutcher: Benj Arriola you did only after contradicting your first sentence
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  Jay Lo: Benj Arriola thank you so much for your elaborate explained!!!
  
  I know set up three of them correctly will definitely help, but just out of curiosity, if I only set up source parameter and no other two, will it technically works?
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  Benj Arriola: David Kutcher that’s right, it wasn’t clear. My intent was to say yes you can put anything there but it’s not ideal. Then I explained what’s ideal. 😝
  
  But anyway, thanks for making it more simple and clearer. 😀
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  Benj Arriola: Jay Lo it may work but you will get a lot of (not set) values in GA. And when medium is not set, it won’t go into the Organic Search Channel in the Channels report.
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  Jay Lo: Benj Arriola I see, so it won`t be counted as organic anymore cuz it will be overwritten as medium_=not set, right?
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  Benj Arriola: Jay Lo correct