It's actually fairly hard to "accidentally" do business with a black-hat SEO. Most of the good ones don't serve clients anyway; they've found they can make a lot more money (with a lot less hassle) promoting their own sites instead of working for (relative) peanuts for clients.
What you're more likely to encounter are SEOs who simply don't know what they're doing, or who are in it just for the profits they can make and have no intention of doing anything useful for your site (because that would be too much like actual work).
Your risk of getting banned or penalized is actually rather low. It's surprisingly rare that sites get banned, and those that do generally really have to work hard at it -- and they almost always know exactly what it was they did that led to the problem.
No, IMO the risk you should be worrying about is that you'll shell out big bucks to some so-called SEO "expert" who won't get you any return for the money. THAT sort of thing happens all the time.
Due diligence is your friend. Learn the basics of what constitutes good SEO. You don't have to
become an SEO -- any more than you have to
become a mechanic in order to buy a car -- but by the same token, most people wouldn't buy a car without at least taking a test drive and maybe checking the ratings in one or more consumer magazines. You have to take the responsibility for doing your homework.
Any good SEO -- no matter what color their headgear -- is going to tell you clearly what he or she plans to do, what results to expect (and how long they should take) and what the risks are. They WANT you to be well-informed and to understand exactly what it is you're buying and to have reasonable expectations of what they're going to achieve. They're not going to promise you the moon and the stars as well, and they're not going to try to convince you that they'll be able to deliver champagne for the price of a cheap beer.
The good ones aren't afraid of telling you the steps they're going to follow because they know it's not WHAT they do, it's HOW they do it that makes the difference. Avoid the ones who hide behind all sorts of technical-sounding (but ultimately meaningless) jargon and can't (or won't) explain to you in simple, plain language
exactly what it is they're going to do, and exactly what they'll expect
you to do.
The good SEOs (white hat and black hat and all shades of gray in between) will be honest with you. They won't make outlandish promises they can't possibly keep. They'll try to keep your expectations reasonable -- which sometimes puts them at a disadvantage against the scammers and incompetents, who offer plenty of smooth talk and slick promises (but, unfortunately, little in the way of real results).
Generally speaking, when someone gets suckered in by a scammer or an incompetent SEO, looking back on it they can see (if they're honest with themselves) there were plenty of warning signs, which they ignored because the so-called SEO was telling them what they
wanted to hear -- that they wouldn't have to make any changes to their website, that they would be guaranteed top 10 rankings, that it would all happen nearly overnight -- instead of what they
needed to hear.
My
--Torka