Mobile UX: Page loads search results quickly, as I click, a sponsored ad generates a moment later, and is clicked instead. Don't want to unroll more aluminum foil about deceptive ad reach spoofing, but...
Less conspiracy related, but being a f500 company and not having your mobile services format mobile keyboard to input field is annoy.
You only accept numbers, only present number inputs.
Tempting a root sanitation bug or propogating poor UX for customers. Either is 