As the title says...
We have a Vsphere 4.1 environment with blades running ESXi 4.1. We are trying to have all the servers share all the LUNs that will host the datastores. Is there a maximum? Are there potential work-arounds? (ESX, hardware, software, etc?)
You are likely to run into other limitations before this one.
For example, the largest datastore you can have is 2TB. If you had 128GB VMs, you would fit 16 VMs on the datastore.
If you had 8:1 consolidation (a conservative number), it would take two servers to run all VMs on that datastore. If you allowed a third for HA, there would be no benefit to allowing more than three servers access to a single LUN.
Many SANs have limitations around how many servers can map to a LUN also - check with your vendor.