Update
I recently discovered you can programatically create selections with Chrome which aren\'t continuous, by either replacing elements /
No, there is no concept of multiple text span selection. The selection is associated with the caret. One caret - one selection.
No. Firefox is the only mainstream browser to support multiple selected ranges. I think the main use case for it was to allow selection of individual columns within tables, which is not possible otherwise.
WebKit are not planning to support multiple selected ranges any time soon, from what I can gather. IE overhauled its Range and Selection APIs for IE 9 and didn't implement it. No idea about whether Opera has any plans to support it. See this thread from the WHATWG mailing list for some information: