None of my contacts use it, so I can't say anything about adoption. But if someone needs to use an IM network - there are good XMPP services. Simply invite your friends to any federated XMPP server and you have an interoperable way to communicate with them.
Explain to them what's bad about walled IM networks (it's like not being able to send e-mails between AOL and Compuserve back in the day) and explain what is the point in the federated XMPP networks. Then explain why Whatsapp security is totally broken. If people won't care after that - just leave them alone. :) Most people understand, but claim they are too tied in the existing walled networks. Some don't mind registering on some XMPP server in addition, so you can get a range of results.
