First of all, unless you really are using alot of vlans on the ESX boxes, its typically better to just put additional network cards as that will also improve vmware performance. It is not that unusual to have 2-3 NICS assigned to each virtual switch. Using VLAN's is more efficient from a network engineering perspective, but vmware systems are meant to use heavy duty hardware and I frequently see systems configured with 8 NIC ports + FiberChannel or iSCSI.

Certainly from a network engineer perspective, this seems to be highly inefficient and thats where the request for 802.1q trunking usually comes in. I believe vmware's reference to loops is really w/ regard to their own virtual switches. Since virtual switches dont connect between each other and virtual machines have their nics virtualized so that there is only one/vlan per vm, there really isnt any way for loops to form inside vmware. That said, I would not turn it off on physical switches. Just use portfast.