Eliezer addressed this in part with his "Death Spiral" essay, but there are some features to LW/SI that are strongly correlated with cultishness, other than the ones that Eliezer mentioned such as fanaticism and following the leader:

• Having a house where core members live together.
• Asking followers to completely adjust their thinking processes to include new essential concepts, terminologies, and so on to the lowest level of understanding reality.
• Claiming that only if you carry out said mental adjustment can you really understand the most important parts of the organization's philosophy.
• Asking for money for a charity, particularly one which does not quite have the conventional goals of a charity, and claiming that one should really be donating a much larger percentage of one's income than most people donate to charity.
• Presenting an apocalyptic scenario including extreme bad and good possibilities, and claiming to be the best positioned to deal with it.
• [Added] Demand you leave any (other) religion.

Sorry if this seems over-the-top. I support SI. These points have been mentioned, but has anyone suggested how to deal with them? Simply ignoring the problem does not seem to be the solution; nor does loudly denying the charges; nor changing one's approach just for appearances.