Can cron write job output to a log *by default* (instead of mail)?
For cronie cron (which is recommended for example by Gentoo Handbook), there is "-s" argument to cron call, which sends the job output to the system log using syslog.
The short answer is no, cron mails to the owner of the crontab by design. In the standard cron there is no way to change this.
The best I can think of is to configure the MTA's on the machines where you want this behavior to dump the mail in to a log file instead of a user mailbox.