Community support is great. It is often speedy, correct, and friendly. However, even if it is like that always, there might be cases when you might need some more formal approach. Common cases when a formal agreement is pursued include:
A company policy requires a support agreement for all systems put in production
You want qualified help when implementing Zabbix
The Zabbix installation will be managed by people who are not deeply involved and don't have great expertise in IT
You need some feature developed or improved
Approaching commercial support is often the best solution in such cases, and it is possible to obtain such a support from the company behind Zabbix software. Visit Zabbix website, http://www.zabbix.com/support.php to obtain more information.
In some cases company procurement requirements might mandate that you use a local company for your support agreement - partner and reseller list at http://www.zabbix.com/partners.php should help to choose one that is geographically close.