Merriam-Webster President John Morse said "w00t" reflected the growing use of numeric keyboards to type words.
"People look for self-evident numeral-letter substitutions: 0 for O; 3 for E; 7 for T; and 4 for A," he said. "This is simply a different and more efficient way of representing the alphabetical character." -- from "w00t" crowned word of year by U.S. dictionary
While I'm rather amused that Merriam-Webster chose "w00t" as word of the year (granted, some two to four years after it really became vernacular for anyone who spent any amount of time online), to suggest that l33t5p34]< and "w00t" in particular is a result of numeric keyboard inefficiencies just indicates how badly Merriam-Webster is stuck in the 20th Century (and don't even get me started on their website).