First, if you're referring to 802.11 WEP (Wireless Equivalent Privacy), WEP has already been broken.

Second, if you encrypt a link, you make it harder for new nodes to join, and the channel key would have to be distributed or made public anyway.

Thirdly, you can't guarantee that your data won't be routed over un-encrypted links, or that the node owners aren't sniffing the traffic that they route.

Using WEP provides a false sense of security, which in itself can be dangerous.

A far better approach is to use end-to-end security. This is where the applications implement the security without relying on the network
(e.g. SSH or SSL (as in HTTPS)), or the hosts under your control create a VPN (virtual private network) perhaps by using IPSec.