I think you should give equity to anyone who's going to have an impact on your team. That's true for engineers, designers and especially marketing people.

Some of the most important people are marketers - however, the best marketers are more product marketers then just a PR / community person.

Equity usually vest over 4 years, so there's 0 risk in issue equity to anyone ... cause if they don't perform, just let them go and no big deal.

Hope that helps.