In a transaction log with too many or too few VLFs we might experience performance issues under a normal workload, as well as during the backup and restore process.
So what is the “right” amount? In customer engagements, I follow a guideline proposed by Glenn Berry of SQLskills.com in his Diagnostic Information Queries, to keep the number of VLFs at or below 200. In my opinion, any number higher than that is cause for concern.
I tend toward the lower number, but if you have a smoothly-functioning environment and some databases have 700 or 900 VLFs, I probably wouldn’t give it a second thought.