What is a reasonable length limit on person "Name" fields?
UK Government Data Standards Catalogue suggests 35 characters for each of Given Name and Family Name, or 70 characters for a single field to hold the Full Name.
I know I'm late on this one, but I'll add this comment anyway, as others may well come here in the future with similar questions.
Beware of tweaking column sizes dependent on locale. For a start, it sets you up for a maintenance nightmare, leaving aside the fact that people migrate, and take their names with them.
For example, Spanish people with those extra surnames can move to and live in an English-speaking country, and can reasonably expect their full name to be used. Russians have patronymics in addition to their surnames, some African names can be considerably longer than most European names.
Go with making each column as wide as you can reasonably do, taking into account the potential row count. I use 40 characters each for first name, other given names and surname and have never found any problems.
I usually go with varchar(255) (255 being the maximum length of a varchar type in MySQL).