No, I've never had an employer that allowed blogging. And even then, I'm not sure I'd be comfortable with the attention given the notoriety of my previous employers.

All I can say is that if you have a choice between a large investment bank and a hedge fund, always go with the hedge fund. They are more agile, more casual, and there's a more direct link between your activities and the organization's profit. Overall, it is more similar to tech.