Like brand-new agents building a client list, brand-new publishers looking for manuscripts can seem like a very attractive prospect, especially to authors who are burned-out on the agent hunt, or have decided to skip it altogether.
However, like new agents, not all new publishers are created equal. The advent of epublishing and the cheapness of print-on-demand technology has made it extremely easy for just about anyone to set themselves up in business as a publisher, whether or not they have any qualifications for doing so. Inexperienced new publishers may not have the skill or resources to acquire, edit, and design books. They may offer terrible, nonstandard contracts. They may have a poor understanding of marketing and distribution, and their small budgets may severely limit any publicity efforts they do make. The consequence for authors: tiny sales, minimal exposure, and, most likely, no professional credit.
There's another risk as well. The attrition rate for new publishers is extremely high, especially if (as many amateur publishers do) they start up without a proper business plan. Inexperienced publishers may not realize that it's best to start with a small list, rather than acquiring books by the handful (overcommitment is a common new publisher problem). They may not know how to evaluate printers or work with wholesalers or manage their budgets (leading to financial problems and logistical log jams). They may be running the publisher in their spare time out of a back room, increasing the likelihood of time management issues and the possibility of getting sidelined by personal or family problems (this is a depressingly common new publisher excuse for nonperformance).
The result: delays, mistakes, broken promises--and, ultimately, closure, often only a few months after starting up. Here's one example, a publisher that opened and closed in six months. There are many more.
Publishers' closures can be a nightmare for authors. While some do the right thing by their writers, formally releasing rights before shutting down (here's one that did this), the more unprofessional or unscrupulous companies may simply vanish, yanking their websites, terminating their email addresses, refusing to respond to letters and phone calls (here's one that did that). Even if a publisher no longer exists, having your rights encumbered by a still-existing, unterminated contract may make it extremely difficult to interest a new publisher in your book. Writer Beware has gotten hundreds of complaints over the years from writers left in this kind of limbo by collapsing small publishers and micropresses.
Also, while very small publishers may not have the assets or the debts to justify filing for bankruptcy, larger ones may. Most publishing contracts include a clause allowing for the return of rights in the event of insolvency or bankruptcy--but authors should not count on this for protection, since bankruptcy courts generally don't honor such clauses. Publishing contracts are considered assets of the publisher's estate, which can be liquidated in order to pay off creditors. If a publisher declares bankruptcy, its contracts are likely to be frozen until the court can decide whether to release or sell them. (This fact caught many authors by surprise when Triskelion filed for bankruptcy last year.)
Obviously, even established publishers can close or go bankrupt--Triskelion was in business for several years before it got into trouble. New publishers, however, are at especial risk, particularly if they're run by inexperienced people (and it can be hard to find the warning signs, since, as Richard pointed out in his last post, it's so very easy to jigger a website).
So unless you are absolutely, 100% positive that the publisher is staffed by people with substantial publishing experience--and maybe even then--it's a good idea to wait until a new publisher has been in business for at least a year, and has published a number of books, before submitting. Not only does this assure you that the publisher can take books all the way through the production process, it lets you evaluate important things like physical and editorial quality, how the books are distributed, and how they are marketed. It also allows time for complaints, if there are any, to accumulate.
Tempting as it may be to join the rush to get in on the ground floor when a new publisher opens its doors, watching and waiting is a much better strategy.