Of course you can always abort the on-site interview early. You don't even have to give a reason, necessarily.
But there's no point to giving a transparently dishonest, "the dog at my homework"-style response, like was apparently done at Twitter in the two occasions cited above.
If I ever heard that piss-weak excuse in an interview ("we can't find the interviewers"? for serious?), I'd be gone regardless. If it's a dodge, it's dishonest and cowardly, and if it's true it displays a shocking degree of disrespect. Either would mean that the culture of the interviewing company was irreparably broken and that I wouldn't be happy there.
