I really hope all of these new restaurants succeed, and that the good ones we have now remain strong. Every restaurant -- every business, actually -- is a very public dream, and it's always disheartening when one fails. I imagine there are plenty of reasons for failure, but I can list a few that haven't been mentioned --
If you're an owner, be honest about your strengths, weaknesses and skill sets. Hire out what you aren't great at, or what you just aren't interested in. ALWAYS hire a good accountant.
Hire good managers (honest, hardworking, team-leaders with excellent communication skills), and let them do their jobs.
Whether you have five employees or 25, run your business professionally. That means policies in place with regard to time off, scheduling, breaks, grievances, etc. Post your staff's schedule WELL in advance! You WANT employees who like to think ahead and plan ahead, so don't run those employees off. There will always be emergencies, but your team will be much more likely to pull together and cover during those times if everything runs smoothly and procedurally most of the time.
There should always be a manager on the floor. If that's not possible then another on-floor employee should be designated as the one in charge of the floor for the shift. Employees should never feel as if no one has their back, that they have no one to help them if a problem arises, that no one cares, that no one is watching.
And finally -- keep your restaurant clean. Please. No one would ever accuse me of being a neat freak, but your standards at home and your standards for public places are different, and people are even MORE demanding of cleanliness at retaurants than at any other type of business. Check those bathrooms every hour. Make sure your front entrance is spotless and all surfaces are wiped down. For heaven's sake, check the front doors and windows for smears on the glass. Take a good whiff when you come in the front door for any off smells. Spread cleaning duties amongst the staff so that no one person feels like cleaning is "punishment" -- cleaning is just part of everyone's job, and no one (from busboy to manager) should be above taking a rag in hand. Where I work, I'm the higest paid employee with the biggest deeeeeeploma, but if the bathroom is dirty, and I'm the one standing there, then I'm the one who's going to clean it!