The Severity field currently allows these values:
Affects Only Me
Affects Some People
Affects Many People
Many people will not be able to effectively answer this question. Further, the choice of "Affects Only Me" implies knowledge that it does not affect anyone else. This is effectively a multiple-choice question with overlapping choices and missing the one value that is often needed.
Patrick Kelsey suggested "Unsure" as the first and default choice, and that makes a lot of sense. Kubilay Kocak suggested "Unknown" which is probably even better. Either of these would replace "Affects Only Me".
This affects "Some People", classify accordingly :P