Why is it a mistake to apply for wide patent protection?

It isn't necessarily a mistake to "widely" apply for patent protection. Where a startup is sufficiently capitalized and has a strategy to aggressively practice the technology in numerous jurisdiction, it may even be acting responsibly to apply for protection internationally. The applications themselves should be broadly drafted keeping in mind that the scope of claimed protection will be narrowed during prosecution. What would objectively be a mistake, as Mr. Weinreib identifies, for you presumably as a practicing entity would be to pursue patent protection (i.e., incur the substantial expense) for technology you would not be practicing, licensing, or litigating-over, or to initiate a broad patent protection campaign without first qualifying your technology's patentability. Your quote "seeking a wide variety of patent protection that later turns out to be unrelated to where the company actually ends up heading" implies a certain absence of foresight on the part of the entrepreneurs (e.g., Are we baking cookies, or are we developing a space elevator? Let's file applications for both!) which in practice should not occur too frequently. It would be prudent to speak with local IP counsel to identify the scope of technology you have, or are developing, and propose an IP strategy that corresponds to your venture's financial predicament and strategic goals.