Mine gets munged with my first name and middle initial happening to form a different name anywhere where names get smashed together -- like plane tickets. Think 'ADRIAN A' vs 'ADRIANA'.

We need you to capitalize that, Mr. Often Truncated.

Same. My last name is 11 characters which is a little long but not that crazy, and my first and middle name are extremely common English names, and yet I can't often fit my full name in places that need it. Usually the issue is on paper forms (especially ones that have specific boxes for characters, which are usually the most important/official ones!), but it's also caused issues in various places on the web and in computer systems before.