I don't entirely agree. As someone who works in a mid-to-large company, and who has worked in a 50,000 person company (admittedly for both companies not all employees were engineers), I feel it's worth noting that as companies get larger and teams more diverse, they tend to require the exact features open source projects need.
A product manager in team X who noticed a bug in product Y is not going to know what fields are necessary for that product, and as issues make their way to company-wide mailing-lists (or are linked from internal meme websites -- you know who you are), they may accumulate +1-spam if no voting system is put in place. As such, I believe GitHub's ability to move upmarket and satisfy its larger customers is actually aligned with implementing the features requested in the "Dear Github" letter.
A product manager in team X who noticed a bug in product Y is not going to know what fields are necessary for that product, and as issues make their way to company-wide mailing-lists (or are linked from internal meme websites -- you know who you are), they may accumulate +1-spam if no voting system is put in place. As such, I believe GitHub's ability to move upmarket and satisfy its larger customers is actually aligned with implementing the features requested in the "Dear Github" letter.