Does anyone have experience doing this? What were you integrating with, and how did you do it?
There is the obvious caution, especially for HTML sources, that your integration may be unstable if the HTML code is periodically updated.
So yeah, what kind of platforms? And what exactly do you mean by no official API?
For example, we've scraped an interactive web site, where we had to use Selenium to simulate a user in order to fill out search boxes to extract all the data.
Is that the kind of stuff you had in mind?