Our cable provider recently boosted our service to 1.4 Gbps, which can be enabled on our Arris modem via LAG: https://arris.secure.force.com/consumers/articles/General_FAQs/SB8200-Link-Aggregation-Setup.
I can clearly see LACP/802.3ad can be enabled for LAN-designated ports on our Balance 580, but not WAN.
This will become increasingly important for us. Similar support is already available from other vendors.