Lean is just consumer research
Well, not quite. The vast majority of consumer research, at least in the brand/agency world, is concerned with consumer behaviour, segmentation, customer perceptions, and trends and the like. It's research that (supposedly) tells you what the world is like based on people's opinions and feelings. However there's a big difference between gaining a world-view and actively testing hypotheses in the field.
Lean is just asking what people want
This is actually the most annoying misperception. Because it allows that ubiquitous smarty-pants in the room to proclaim that people don't actually tell you what they want, and if they do, it will be wrong. Yes, we know this too! It is indeed true, and most definitely not rocket science. A real customer development approach does not ask people to say what they want, instead it variously and iteratively discovers what they actually want using participatory tools such as sketches, prototypes, use cases, user journeys, demos and more.
Lean is boring and formulaic
In truth, no two Lean Startup processes are the same. While it is more akin to a scientific process (ie formulating and testing hypotheses), my experience is that this makes things feel like a detective novel where you have to follow subtle clues and be open to twists and turns. Whatsmore, it is in no way clean or easy. Cath wrote a cracking post where she confided that the truth is that these things are actually very messy and "if it doesn't hurt, then you're doing it wrong".
Lean is simply doing things cheaper and faster
While this is a frequent happy outcome, it is not in itself the case. As this wiki page about lean startup misconceptions points out:
Customer development, one of the key principles of the lean methodology, takes time. There is no way to predict how long it will take to refine the hypothesis into a problem worthy of solving and then to create a solution worthy of being sold. In addition, the solution may turn out to be expensive to build.
Lean and Agile: same diff, yeah?
I admit it's confusing that terms such as L/lean and A/agile are used in so many different contexts and ways. For starters they can both be nouns and/or verbs. And while Agile is certainly a broader philosophy than just a manifesto for software development, I think Agile works best as a waste-minimising way to execute known solutions, as well as a being a flexible and adaptive to execute unknown solutions. However traditional Agile practice does not really help in understanding and exploring the problem space. That's where Lean Startup thinking comes into its own: helping you out of that terrifying place where you don't even necessarily know what the problem is.
Lean is stupid because Apple doesn't do it
If you have $40 billion in cash lying around, an auteur/genius CEO with decades of experience in making successful (and unsuccessful products) not to mention a plethora of brilliant technologist employees all around the world, then maybe you don't need to get the business model generation tool out at your company meetings. I would argue however that Apple employs a range of tools that are lean by any other name. They test stuff constantly, albeit mostly hidden from the public's prying eyes. And they also iterate like crazy… even if they do have a philosophy more around Maximum Desirable Product versus Minimum Viable Product.
Lean is the enemy of creativity and intuition
Only people who haven't practiced lean would say this. Designing a Lean Startup process requires extraordinary creativity and imagination. Deciphering clues, deciding what and how to test things, recognising when to iterate versus when to pivot, all requires great intuition and judgement. It is true that a lot of the focus around lean UX is more about optimisation, but high level Lean practice includes the possibility of making intuitive leaps beyond the micro-focus of iterating.
So what is lean?
For what it's worth, I think the simple power of the lean startup philosophy is as a 'super validator'.
It's a means of efficiently finding out whether ideas are actually any good. It's powerful because it sidesteps the ego-centric obsession with 'coming up with a Big Idea' and instead encourages a space where 'small ideas' can be tested to see whether they actually have the potential to be successful (why is a "big idea" good anyway?).
It's in this creative machine-like capacity as a 'super validator' that lean delivers the simultaneous business benefits of efficient opportunity exploitation and risk mitigation.
It sounds simple enough, but I can assure you, it isn't necessarily easy being lean. But of course that's part of the enjoyment of trying to do things in new ways.
I'm sure there are plenty more misconceptions about what Lean Startups thinking is really about, so I'd welcome your comments. And for the record, I am well aware of the unfortunate perception that lean (in the words of my esteemed colleague @higgis) is simply "the latest trendiness being pushed by a bunch of cocky hipsters." Suffice to say I don't think that is the case, though I'm happy to concede that simply drinking Eric Ries' Kool-Aid doesn't necessarily make you lean.
[Huge thanks to MxM's brilliant @alex_r_harding's and his awesomely fun illustration!)