Liberals believe in equality of opportunity.
Socialists believe in equality of outcome.
At times, these interests converge enough to allow for a coalition, but they are distinct.
Sorry to be so pedantic, but this is one of my pet peeves.
References:
http://en.wikipedia.org/wiki/Liberal
Broadly speaking, liberalism emphasizes individual rights and equality of opportunity
http://en.wikipedia.org/wiki/Socialist
Socialism refers to a broad array of ideologies and political movements with the goal of a socio-economic system in which property and the distribution of wealth are subject to control by the community
