You can only change it for admins as far as I can tell. Here are some other things that affect how much reputation you can give/take from people
Register Date Factor (set at 365. I think that's kinda ridiculous)
For every X number of days, users gain 1 point of reputation-altering power.
Post Count Factor (1000 I guess that's about right.)
For every X number of posts, users gain 1 point of reputation-altering power.
Reputation Point Factor (100. I guess that's fine.)
For every X points of reputation, users gain 1 point of reputation-altering power.