There has to be some sort of selection criteria - new teams need to prove they have the financial and human resources to succeed in F1. That doesn't mean they have to win a championship in their first year. What it means is they have to show they can succeed on the track and meet basic financial requirements ie they can pay to get real F1 drivers.
This is what I have been saying in other threads; if a 13th team was not allowed to enter F1 because the potential teams were not financially viable, at the start of the season all teams should be able to show financial stability to bring two race cars to each and every race of the season with non-pay-drivers in the cars.
They should also have some history, competing at some motor racing level with success.
I could be wrong on this but didn't Campos Meta (who later morphed into HRT) have previous race pedigree in lower formula?
I've read some points raised here and in other places that F1 should help the bottom teams. Well, I think there might be some validity to that, IF, those teams had met the criteria above. But honestly, letting "mom and pop" teams into F1, no amount of help is going to get them into F1 shape.....
The issue is that when these teams joined the F1 circus; that was amidst promises of a budget cap of €40m and technological help from the bigger teams, neither of which happened; at least not in their first season, Lotus are now getting help from Red Bull and HRT are getting Williams gearboxes.