The user in whose name the cron job runs doesn't have permission to execute wget, or to write to /dev/null.
if wget permissions:
I guess this is because you are on a shared server
First of all check that you can run this command directly from the shell (if you have shell access). If you cannot, then you may have to run this periodic webpage request from another machine. This is what I do on my shared server - request the webpage from a machine where I have full permissions to add jobs to crontab which execute whatever I want. You'll want to check that this machine has high network availability and uptime, though since it effectively becomes part of your moodle installation.
if /dev/null permissions
Change your command line to remove the output to /dev/null. I believe that -q removes any output from wget anyway, so your command line looks like...
wget -q http://bunch-of-families-in-sapporo.eflclasses.org/admin/cron.php
I suspect that the problem is the way that information is written to /dev/null, which occasionally causes permissions problems if you address it directly, so this second command line should work OK.