Link aggregation, aka "trunking", is similar, yet different to IP multipathing (IPMP). Both actually let you increase outbound bandwidth by spreading it across multiple links. Both give you a measure of automatic failover support. However, only link aggregation lets you spread inbound bandwidth across multiple links.
That's the good news. The bad news is link aggregation has some important limitations that, while they may not be a problem in "small to midsize" shops, can be a problem in enterprise level endeavors.
Link aggregation uses the IEEE 802.3ad protocol, sometimes known as LACP. This makes it an Ethernet-only solution. An even stronger limitation is that all the links that are aggregated together must be on the same switch.
In contrast, IPMP, can be used across truly redundant, separate switches. Furthermore, as it is an IP-level solution, rather than a link-level solution, it can be used on top of alternative transports such as InfiniBand.
The bonus good news, for...