The long-s was a remnant of the Roman, Latin, cursive, lowercase letter s (the s used to be called the terminal-s, round-s, or short-s), and its use wasn't likely much of a problem before widespread use of moveable type and widespread literacy. Now, though, it's completely disappeared in contemporary English, to such an extent that trying to read a paragraph in which the long-s is used becomes very difficult for some. (Of course, reading Chaucer is a few steps more difficult, but that's something for another post at some time.)
Of course, for people being introduced to the long-s, people must first learn the rule of how to use ſ, which - in English - was basically used for all cases of s, except at the end of a word (e.g., his, cats), as the second s in a pair (e.g. ceſsation), and when paired with an f (e.g., ſatisfaction).
Therefore, if we were to continue to use these rules, the previous paragraph would be written as:
Of courſe, for people being introduced to the long-s, people must firſt learn the rule of how to uſe ſ, which - in Engliſh - was baſically uſed for all caſes of s, except at the end of a word (e.g., his, cats), the second s in a pair (e.g., ceſsation), and when paired with an f (e.g., ſatisfaction).The use of ſ was phased out of English over time, and the last official use of it in official US documentation was in the 1803 Acts of Congreſs.
For more information: http://en.wikipedia.org/wiki/Long_s