This means highlighting will simply not happen (with no explanation to the user) on longer documents.  Should we consider raising the limit at least?  Seems worth doing a litle perf testing, at least.

Also -- I wonder if the limit should really be based on _chars_, not lines... assuming the motivation here is that searching lots of text is too slow, a compacted file with only 10 lines but 10,000+ columns wide is equally likely to be problematic.  (I did a quick test using jquery-1.7.min and it sure runs like a dog on that file!)