Firewalls these days are packed with wide range of UTM capabilities like IPS, anti-virus, application filtering and web filtering. All these features might add huge constraint on the device itself, as they require higher CPU and memory resources than simple packet filtering by ip addresses and port numbers.
This might become an even bigger problem if you have a small edge/branch firewall which has much more restricted resources.
Of course, upgrading a firewall is a one-shot solution, but it usually costs too much, especially considering that these small firewalls are installed on the smaller branch offices.
Firewall bursting might come in handy in this kind of situation by sending the resource heavy tasks to the cloud and keep the hardware busy only with the lighter tasks such as simple packet filtering and routing.
This is a fairly new concept, but considering the fact that the “cloud” is the magic word in the IT industry these days, and firewalls are getting more and more constrained under the heavy duties like packet decryption, IPs, antivirus and proxy; this can be a huge thing in the near future.