If this propery is false, OnEventName methods will also not be called. Also, you'll be unable to check verification statuses of e-mail addresses in the bulk as Verified event will not be called. Setting to false can make sense only for debugging purposes.
If you get lockups when enabling events in WinForms apps, the message loop of your application may be blocked. If you cannot unblock it for some reason, consider inheriting EmailAddressValidator class and overriding OnVerified(VerifiedEventArgs) method.