Identifying Fault Tolerance use cases is a part of the VCP 4 exam blueprint-- and digging through some of the VMware docs, this is what VMware considers use cases:
<ul>
	<li>Applications that require 100% uptime, especially those with longer-term connections that must be maintained during/after a failover event</li>
	<li>Customer applications that have no other way of clustering</li>
	<li>Cases where high availability may be offered through customer, highly complicated clustering technologies that are difficult to implement/maintain</li>
</ul>
They also mentioned &quot;On-Demand Fault Tolerance&quot;, which is essentially turning on FT when you feel it is most necessary. The example they give is if your company is running it's end-of-quarter reports, and they have a strict deadline of being finished, you can protect the VM by enabling FT and then simply disabling it once completed.