I have to express dissent with the supposition people need to 'back up' a personal experience on an interpersonal site given a number of huge flaws:
Studies are not real life experiences
Taking polling data, asking a group of people if they would do XYZ, referring to some scientific citation or claim (which may be absent other citations or claims due to funding, etc) are often very poor indicators to real world experience, especially across broad gaps in culture.
Citations are for skeptics, not socialites
The indication for 'sources' or 'citations' is more an attitude I'd expect on skeptics. Bearing in mind these are engagements that often involve heavily opinionated, heavily nuanced social manouverings, asking for a citation for that one time you managed to write a convincing letter that got a person to stop doing a thing seems capricious and overly burdensome. A 'your mileage may vary' disclaimer applies to all suggestions, and none will work always no matter how many sources.
Citations have zero bearing in opinionated subjective interactions
Can you imagine how social interactions would sound so weird if they were citation centric: 'I know I'm right because I can cite Webners 1978 study into the social interactions of mice'. I'm sure the very angry burly dude understands and isn't going to get narked off.
Extrapolation is not accuracy or credibility (AKA they can just lie further)
Asking for a further explanation, especially of an intrinsically logical or 'self-evident' thing, doesn't guarantee any further accuracy or probability of success. For example, if I'm evil troll(tm), I will spin whatever tale I need to 'back up' my dubious claim. Heck, I could probably misquote, miscite, or acquire cherry picked studies to backup whatever I'm going to say.
Back it up is a solution to a not very clearly defined problem
It's unclear to me what the 'back it up' policy is trying to solve problem wise. Is it to stop trolls? You're always going to have trolls. Is there some massive problem of people giving out bad advice that doesn't work (why the large number of upvotes?)? Genuine, but bad advice, is still going to be based on in-world experiences (and thus, citable); trolling and bad advice can be twisted to fit whatever paradigm.
All things are subjective anyway
Perhaps instead, a different policy: a disclaimer on why a set of advice is bad? Deleting the advice only merely means others under the same illusions will see that it's missing and then proceed to recreate it.
It doesn't set a positive tone
I've had a bad experience of the back it up policy so far: my first contribution on a question riddled with variations of people suggesting the person 'accept' or 'comply' with something they weren't inclined to do, was based on my personal experience of 'politely declining' something. Surprisingly enough, I was asked to back it up, which then promptly entailed downvotes. I'm baffled no-one on IPS is familiar with the concept of making a polite declination to an offer, which included an explanation on how to make one.
I was asked what experience I have with declining the absolutely specific item on the question (business card). This seems a bit strange to me, given there's no evidence of declining one thing (a business card) is any different from, say, a flier, or a gift. I could pick any number of examples of politely declining something, as could anyone: why is it even necessary? What does one hope to gain if I re-explain my suggestion for a second time in an anecdote?
Authority isn't sociability
The ability to navigate the social waters isn't predicated on one's authority, job title or position, but one's own interactions and experiences. What do you call a highly qualified socialite? You don't.
If this is about 'context' of the situation (male, female, old, young, country, culture, etc), then the message of 'back it up' is the wrong message. Backing something up implies adding credibility, with the implication you're not trustworthy. Where-as asking for context asks for a user to expand on additional details.
I'm going to be ironic here and cite a few studies why studies are bad:
Psychology studies generally not reproducible:
Why scientific studies are often wrong:
Fraud and misconduct in studies: