The thing about bangs is that it's a curated, auto-updating list of shortcuts though. I could install my own but with ddg, I just throw a ! in front of the site and usually it works!
!gh { https://github.com/search&q=$QUERY$ }
!ebay { http://www.ebay.co.uk/sch/i.html?&_nkw=$QUERY$ }
Then all browsers (and other apps) could provide these standard shortcuts in their search functions.Reading the site though, it seems poorly adopted? And also not automated (the user has to actively install SearchProviders? Most users don't bother.)