Depends on what you mean by proxy. There are what's called 'reverse proxies' that sit in front of web servers and field requests as a form of load balancing. See Wikipedia link below.Now, there are also what's called Onion Routers (like Tor) that allow you to host services (anything, including websites) via an anonymous proxy, however, to get to these services they require that you run through a Tor (proxy).Depending on what you think a phishing site may gain by using proxies (load balancing, or a as a way of hiding identity), I'd say it's being done, but primarily via nefarious means, such as forwarding across another network in an attempt to either appear to be someone else or to obfuscate who/where/what the true site may actually be.There are also other manners of tunneling and forwarding that can be used to make a server or service appear to be in one place, yet actually be in another.
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