What made Italy turn from the Triple Alliance to the Entente?

What most historians say is that Italy turned away from an
alliance with Germany and Austria-Hungary and toward an alliance with France and Great
Britain out of greed.  The Italians claimed that the change was due to the fact that the
Germans and Austria-Hungary had been unfair to the Serbs.  But historians say that this
was not the real reason.

Before the Italians switched
sides, the British, French and Russians made a secret treaty with them.  The basic idea
of this treaty was that the Italians would get a lot of new territory.  Specifically,
the Italians were going to be given (if they joined the Allied side) a lot of territory
that they wanted but which currently belonged to
Austria-Hungary.