I noticed that Ola Hallengren's backup sp has backup checksums disabled by default. This made me curious to know if there are any potential cons (i.e. increased CPU, IO, long backup times, etc) associated with enabling backup checksums for sql server backups?
Yes, and you can verify that on the Backup Checksums doc:
Due to the overhead verifying and generating backup checksums, using backup checksums poses a potential performance impact. Both the workload and the backup throughput may be affected. Therefore, using backup checksums is optional. When deciding to generate checksums during a backup, carefully monitor the CPU overhead incurred as well as the impact on any concurrent workload on the system.
But I advise you not to discard the checksum benefits just because of the cost it implies. Check the documentation to better understand the checksum and then decide whether to use it or not.
That same doc states that
after encountering a page checksum error, a BACKUP or RESTORE operation fails and a RESTORE VERIFYONLY operation continues.
As you can see, when using checksum it's possible to find out that your backup is not reliable while taking it and not when you need to restore it (you don't wanna find yourself in this situation).
The reason checksums are not enabled by default in the backup stored procedure DatabaseBackup is just to follow the defaults for the backup command. I strongly recommend you to use checksums. @CheckSum = 'Y' is also added in the jobs that comes with the installation script MaintenanceSolution.sql. – Ola Hallengren