DBCC CHECKDB - Corrupted Pages On my understanding, regular run of DBCC CHECKDB is a best practice in order to check integrity of the database.

If there comes a time where a corrupted page existed, and no good back up is available, in general, what are the consequences can occur? Nothing? Corruption will spread?
DBCC CHECKDB will also run DBCC CHECKALLOC, DBCC CHECKTRABLE, and DBCC CHECKCATALOG. 

Running this regularly is extremely important in an effort to detect data corruption. If availability is important, you should consider running this daily. It is possible for backups to contain corrupted data as well. This can easily go unnoticed if the corrupted page(s) isn't accessed. Corruption can occur due to several factors including: storage configurations, power faults, poor cache, etc. 

It is possible for corruption to spread, so be prepared! Your system and user databases should be backed up frequently with CHECKSUM and the databases be configured with the Page Verify setting set to CHECKSUM. 

I would take a look at Kendra Little's post on the issue.

Brent Ozar also has a post regarding what to do when DBCC CHECKDB reports corruption. 

Steve Stedman also has an excellent Weekly Database Corruption Challenge if you wish to attempt repairs.