In non-english languages, it is frequent to be restricted to 70 characters/SMS following usage due to a character not fitting in the 7bit GSM Alphabet[0]. When going over, the handset has to switch to UTF-16 (2 bytes per BMP character, 4 for non-BMP characters)
Comments
The reason 140 was chosen had to do with SMS limits 160 chars). A 140 character limit left enough slack to allow metadata to be sent.
SMS has a limit of 140 bytes, not 160 characters.
In non-english languages, it is frequent to be restricted to 70 characters/SMS following usage due to a character not fitting in the 7bit GSM Alphabet[0]. When going over, the handset has to switch to UTF-16 (2 bytes per BMP character, 4 for non-BMP characters)
[0] http://en.wikipedia.org/wiki/GSM_03.38