Hey trunks, the major limiting factor in versions of LEM prior to 5.6 was the database architecture. It couldn't be expanded to more than 1TB. In 5.6 with the Lucene foundation (thanks prawij!) the sky is the limit...except that VMWare and HyperV (until very recently) only allowed a virtual machine to expand to 2TB.
However, VMWare has released a new version of ESXi and VSphere. If you take a look at this doc from VMWare, page 12:
"vSphere Storage Enhancements
VMware is increasing the maximum size of a virtual machine disk file (VMDK) in vSphere 5.5. The previous limit was 2TB—512 bytes. The new limit is 62TB. The maximum size of a virtual Raw Device Mapping (RDM) is also increasing, from 2TB—512 bytes to 62TB. Virtual machine snapshots also support this new size for delta disks that are created when a snapshot is taken of the virtual machine." - What’s New in VMware vSphere® 5.5 Platform, Document Version 1.3, Retrieved Nov 15 2013
And Microsoft has improved HyperV in Server 2012 and Windows 8:
"Virtual hard disk capacity:
64 TB supported by the VHDX format introduced in Windows Server 2012 and Windows® 8; 2040 GB supported by the VHD format." - Hyper-V Scalability in Windows Server 2012, Updated June 24, 2013, Retrieved Nov 15 2013
Which means you can theoretically throw 62TB at a 5.6+ version of the LEM, it will see the new disk space, and busy itself growing to fill that space. That's a LOT of data! So the limits in 5.6+ are more dependent on your platform and available resources than anything else now.