Explaining to New Investors Why "Comps" From Trulia & Zillow are Not Reliable

[Samantha M.]

As the topic states, sometimes when I speak with individuals new to real estate they will often site Trulia and or zillow to pull comps.

Thats not for a general estimate mind you, but for actual comps for the subject property.

How do you explain that such sources are less reliable than the MLS? To my knowledge, trulia/zillow use some sort of algorithm that aggregates prices. In other words, its decent for a "ball park estimate" but for specific comps its no good.