Recently, I wanted to compare the lists of off-topic things on /tour across all sites on the Stack Exchange network. My first instinct was to look to see if those lists (which are proper markdown-enabled posts) were available in the Data Explorer, and indeed they were: here's the list for Meta.SE.
The problem is, these posts are of PostTypeId = 7 "WikiPlaceholder", and they're not the only posts of that type. Most sites have up to six of these posts (besides Ask Patents, which apparently has 18), only one of which is the list of off-topic things. Now, since six isn't a large number, I could just pick out the list of off-topic things manually, but this would be a chore if I had to do this for all 150ish SE sites.
So instead, I wrote some code to scrape /tour on all SE sites like a caveman (see results here if you're interested; we have the unique distinction of being the soup-nazi-est site on the network by this metric).
If it were possible to identify different types of WikiPlaceholder posts in the Data Explorer (without manual intervention), I could've just run a query instead and hence gotten those results in a less-cavemannish way (and, plus, this way, the code lives in the Data Explorer, which is more easily accessible than dumping a Python script with non-stdlib dependencies into a gist or whatever). Maybe this entails adding new PostTypeId's, or maybe a new column called WikiPlaceholderTypeId, or something; I dunno.