Even when you follow The Mom Test rules, bad data can sneak into your conversations. Fitzpatrick identifies three types of bad data that poison customer learning: compliments, fluff (generics, hypotheticals, and the future), and ideas. Recognizing and deflecting these is essential to getting conversations that actually matter.
Customer conversations go wrong not because people lie deliberately, but because certain types of responses feel informative but contain zero useful signal. You need to learn to spot them in real time and steer the conversation back to solid ground.
“Compliments are the fool’s gold of customer learning: shiny, distracting, and entirely worthless.” — Rob Fitzpatrick
Compliments are the most dangerous form of bad data because they feel so good. When someone says “That’s a really cool idea!” or “I love it!”, your brain lights up with validation. But compliments contain no usable information. They tell you nothing about whether someone will actually change their behavior or spend money.
How compliments sneak in:
How to deflect: Do not accept the compliment. Bring the conversation back to their life. “Thanks — but can you tell me more about how you are handling this currently?”
Fluff is any statement that is not grounded in concrete past behavior. There are three sub-types:
All three sound informative but contain no reliable signal. People are terrible at predicting their own future behavior. The only reliable data is what they have actually done.
How to deflect: Anchor everything in specifics. “You said you usually do X — can you walk me through the last time that actually happened?”
When customers start suggesting features or solutions, it feels like you are getting valuable product input. But feature requests from customers are almost always bad product direction. Customers are great at identifying problems but terrible at designing solutions.
When someone says: “What you should really do is add a feature that…”
How to deflect: “That’s interesting — what would that let you do that you can’t do now?” This brings the conversation back to the underlying problem, which is what you actually need to understand.
Learning to redirect bad data back to useful territory is a core skill. Here are the key deflection patterns.
They say: “That’s so cool!”
You say: “Thanks! So who else have you seen trying to solve this?”
They say: “I’d definitely use that.”
You say: “When was the last time you looked for a solution like this?”
They say: “Shut up and take my money!”
You say: “Great — let’s talk about setting up a pilot. What would we need to do on your end?”
The key is to never let a compliment end the conversation. Always follow up with a question that forces specifics.
They say: “I always struggle with invoicing.”
You say: “Tell me about the last time that happened. What went wrong?”
They say: “I would definitely pay for that.”
You say: “How are you currently solving this, and what does it cost you?”
They say: “Yeah, I’m going to switch to a better tool soon.”
You say: “You mentioned that — when did you first start thinking about switching? What have you tried so far?”
The deeper problem with fluff is that it can contaminate your entire understanding of the market. If you collect a dozen “I would definitely use that” responses, you might feel like you have validated demand. But all you have is a pile of empty promises.
“The world’s most deadly fluff is: ‘I would definitely buy that.’” — Rob Fitzpatrick
Every fluffy statement can be converted into a concrete question:
Fluff: “I always forget to follow up with leads.” Fact-finding: “When was the last time you lost a deal because of that? What happened?”
Fluff: “I would pay $50/month for that.” Fact-finding: “What are you paying for your current solution? Have you looked at alternatives?”
Fluff: “That’s a huge problem for our team.” Fact-finding: “How much time does your team spend on this per week? Has anyone tried to fix it?”
Not all data is verbal. Pay attention to emotional signals — moments when someone gets visibly frustrated, excited, or embarrassed while describing their situation. These emotional spikes often point to the most important problems.
These behavioral signals are far more reliable than any verbal promise.