Not true. Registering stock so your business can trade publicly isn't all that expensive. You can start with an S-1 or a 10-12g. The process may take from six months to a year or so, but it's not such a big deal if you're serious about building a business.
Should people take a company public with just an "idea"? No. They should be DOING something, not merely imagining that one day--after they try to pump their brand new stock--they might.