Personally, when I say "excuse me" on the pavement, I'm being sincere :) the space is no more mine than it is their's. But, I think all of this varies based on the culture of your immediate surroundings (for context, I live in London, UK). After all, "excuse me" could only be used ironically, if its genuine tone was apologetic (at least somewhere). I also have heard "pardon me" used interchangeably with "excuse me" in the ironic sense (usually to feign not having heard an offensive remark).