I can get a 7.1/768 DSL circuit in Los Angeles
I'm going to try to start a MAN using many of these circuits

Am I crazy???

Any advice on why or why not, what to do or not to do?

Any help would be greatly appreciated

Many people use DSL. There are various types of connections. You need to verify with the Provider that your intended use does not violate their TOS. You need to make sure they offer some type of SLA or uptime guarantee. You also need to findout if the bandwidth is guaranteed in any way, or if it is a 'best-effort' service.