Seems like an interesting enough read, and even if there is possibly going to be a Binance bias, bearing that in mind, it’s still rather informative, even if we presume it profiles with better exactitude their customer base.
<…> 1. The methodology doesn't mention how they contact the crypto user.<…>
They mention some of the specifics here:
https://research.binance.com/en/analysis/global-crypto-user-index-2021:
Distribution of the survey
The survey was translated into eight different languages (English, Spanish, Russian, Turkish, Chinese, Vietnamese, German, Dutch) and disseminated via a web-based questionnaire for a global audience, along with a dedicated survey for the Chinese market.
The respectively used channels included:
• Social networks (e.g., Twitter, Telegram, Kakaotalk, VK, WeChat)
• Reddit forums)
• Direct emails to Binance.com users
• Banners on Binance.com and CoinMarketCap.
Later on, within the above link, they mention some of the basis of their methodology, from which reading I infer that some of the data is cooked in order to try to better represent the survey population (i.e. as they do with voting intention poll, where we do not simply see counts). Every page on the survey includes a footnote with specifics considered for the question being treated.