In the general case, equity could serve to create a realistic in-between position between employee and partner. An employee with equity might not have control or responsibility for the entire business, but they have a more direct stake in its success. So there's that.
In this specific case, Penny Arcade's job offer doesn't mention anything about equity. Their IT guy won't be part of their branding or image, so they don't even get any social equity out of the deal. The IT guy would be an employee, who'd be expected to expend effort like someone who's bootstrapping the business.
There's nothing wrong with adding a partner. The family farm adds (and loses) partners every generation. Having an extra partner can be great, and it's perfectly reasonable to prefer a partner to an employee. (Or vice versa.) If what you really want is a partner, then you'll be a lot happier if you find a partner and treat him as such.
If, on the other hand, you do not really want a partner, you should be honest with yourself about what you are looking for. Maybe you really want two or three employees. Maybe you need one full time employee and a few part time employees. Maybe you need some combination of employees and contractors, who can respond to extraordinary problems and then go away when there is no work to do. (IT tends to have a problem with the latter. It's like expecting the cleaning staff to do plumbing just because you don't have enough plumbing jobs to keep a plumber on staff, and they both work with bathrooms.)
To sum it up with a bit of sexist humor, if what you need is a wife, either find a wife or hire a cook, a maid, an accountant, and a mistress. Don't hire a cook and expect him to sleep with you and do your taxes.
In this specific case, Penny Arcade's job offer doesn't mention anything about equity. Their IT guy won't be part of their branding or image, so they don't even get any social equity out of the deal. The IT guy would be an employee, who'd be expected to expend effort like someone who's bootstrapping the business.