As sites are built different code is included for different browser engines as they tend to process information differently. Being able to mask ourselves as iphone (et. al.) just gives us another way of accessing the information if the standard browsers have bot blocking code, flash images, complex coding and/or are otherwise difficult to scrape. Smart phone browsers are based on much simple engines and I've always looked at that as kind of a back door for us botters... one that has saved my bot's collective asses on many occasions...