it would be nice if an agorist would comment here... in the meantime:
apparently agorists call themselves leftists because they see their theory/plan as rejecting hierarchy and reducing social inequality.
if you define the left that broadly, then i guess that works.
anarchopedia says that some consider it to be an attempt to bridge anarcho-capitalism and anarchy (an effort i can only be hostile towards).
from anarchopedia: Government favored corporations are viewed by Agorists to link the illegitimacy of the state to many such businesses. State restrictions that limit liability on corporations are believed to corrupt those businesses such that the upper management acts irresponsibly with corporate assets. For example, if such businesses excessively pay executives and are then unable to meet contractual debts, many state laws protect the wages of those responsible for the bankruptcy. Agorists argue that liability cannot simply disappear by act of government and so legitimate business will always have managers or owners who will be held responsible for any actions taken.
Corporations are considered to be allied to the "political class", as they cultivate, support and benefit from the existence of the state. Corporations are regarded as being in possession of illegitimate property accumulated through coercion over a period of time. For this reason, Agorists support the takeover of corporate property by the workers as an act of homesteading, an idea initially proposed by Murray Rothbard, who only retreated from the position after being unable to propose an effective system for the redistribution of property that didn't rely on the state or mindless violence. However, though Rothbard backed down from the position, the idea has been carried on into Agorism.
so in the above, the leftism is in not favoring the executives over workers or people who are owed something by contract, workers being able to take over through homesteading, etc.
i would certainly argue that regardless of left or right (and perhaps as an example of the limitations of left/right thinking), the ramifications are not desireable, but maybe if the goal is a) to be practical about people exchanging things in a post Huge Change world, and b) to imagine how that might work, and c) to recognize that small markets are not necessarily the expansive nightmare that capitalism is... then it would seem harmless to the extent that anyone planning for society-wide structures could be harmless.
ps: we should have a question here about what characterizes The Left... (or maybe we do and i've forgotten it).