There is limit on the number of VPN peers, which is the same thing really. Check your license features by issuing the below as the cli:-

show ver - you should see something like:-

Licensed features for this platform:

Maximum Physical Interfaces : 3

Maximum VLANs : 10

Inside Hosts : Unlimited

Failover : Disabled

VPN-DES : Enabled

VPN-3DES-AES : Enabled

Cut-through Proxy : Enabled

Guards : Enabled

URL Filtering : Enabled

Security Contexts : 0

GTP/GPRS : Disabled

VPN Peers : Unlimited

The VPN peers is what you are looking for - numbered or unlimited! There is an encryption thru-put limitation you can't have a million tunnels and expect to get Mbs of thru-put!

HTH.