Final answer:
A major mistake for blogs concerning mobile and social experience is failing to optimize for mobile usage and integrate social media features, which can hinder user experience and content reach.
Step-by-step explanation:
A big mistake on blogs when it comes to mobile and social experience is not optimizing for mobile and social media integration. When blogs first entered the online scene, they were a platform for individuals to share content without needing the technical skills to own a domain or code a web-site. The evolution of social networking sites, like My-space and later Fac-ebook, democratized web content creation even further, making it extremely easy for anyone to have a web presence.
However, as technology evolved, the importance of optimizing for mobile devices became crucial, especially in terms of layout, design, and readability on smaller screens. Additionally, integrating social sharing features has become important for wider content distribution and engagement. Failure to consider these aspects can lead to a poor user experience and reduce the reach and effectiveness of a blog's content.