>If we take your original statement and change "browser" to "search engine" and "IE" to "Google", we end up with this: "If any single search engine had the mark

>If we take your original statement and change "browser" to "search engine" and "IE" to "Google", we end up with this: "If any single search engine had the marketshare that Google had in its heyday, it would be irresponsible and anticompetitive for them to implement nonstandard features." If Google made non-standard extensions to robots.txt, that would be an equivalently anticompetitive situation. To my knowledge Google hasn't done anything like that. We are not talking about just any features here, but features that make websites incompatible with other browsers. Search engines, by and large, are not concerned with interoperability in the first place, so your analogy is nonsensical.