Back in the day, when the Internet was new and the powers-that-be in cyberspace didn't know how to build a serviceable Dewey Decimal System (of sorts) to help visitors quickly find the information they were looking for online, they came up with SEO--search engine optimization. SEO-based searches worked well for a while, right up until unscrupulous web content producers (clueless copywriters and hired hacks) began to behave badly, stuffing SEO keywords and phrases into their copy with total disregard as to whether they were providing anything else of value. As long as the keywords boosted their sites to near the top, they felt their jobs were done. So what if the rest of the information on the site was crap? It wasn't their job to write helpful, seeker-friendly copy, was it? They'd been hired to boost rankings, to get seen topside on Google and other search engine sites, not to get visitors to stay and play.
The result? You remember, I'm sure. When you'd go looking (for example) for a "Tacoma copywriter" the first several pages of returns were all about, "Learn to be a copywriter," "What does a copywriter do?" "copy writing defined", etc.
What you'd get were ads and definitions, not a single name for a Tacoma copywriter. It was frustrating as hell.
Back then, you got that result because a bunch of people calling themselves internet writing gurus figured out how SEO worked and started stuffing SEO-friendly keywords and phrases into the copy they wrote to divert seekers to their employers' websites, even though the sites were rarely allied with what you were looking for. So you'd find yourself scrolling down the page, often page after page, until finally--maybe!--you'd find an actual Tacoma copywriter with a name, website and phone number. Hallelujah! But it took for-freaking-ever!
Google developed the Panda and Penguin algorithms (and most recently as of this writing, Hummingbird) to weed out the black hat operators who were/are abusing their filing system. Google's goal, always, is to point seekers to the sites that are most likely to satisfy their needs. Google isn't in business to mislead and frustrate its users; it's in business to stay in business and, to do that, it needs to help weed out the cheaters.
So a lot of SEO firms and copywriters (and, sadly, their clients/victims) that are adversely affected by algorithm changes more or less "have it coming to them". They "cheated" their way to the head of the class under the old system and they've been caught red-handed.
Good copywriters have never had to worry all that much about algorithm changes. Good copy is "sticky"; that is, it's helpful--when people find it, they stay and play, stay and read, stay and buy. In a nutshell, they find what they're looking for.
This is why, in a world filled with self-proclaimed and unregulated SEO companies and copywriters, it's always good to seek proof that the company, entrepreneur or writer you're thinking about hiring has a clean record, pre-Panda and Penguin and post-Panda and Penguin. Ask to see the sites their work appears on and ask how long they've been there. If their sites are still high and dry, toward the top of search rankings after each of the algorithm changes, you can feel pretty secure that they're doing things the right way and serving you well. They're making sure that the sites they build and the copy they write for you will be enjoyed and used by the people who are looking for what you do.
If they can't produce proof of their SEO acumen pre- and post- algorithm changes, maybe they don't have any. And that should be a red flag to you.
Another thing. Some SEO companies have you pay a lot of money for monthly "services" to make sure you continue to rank well. Just a word to the wise: a well-written website doesn't require monthly monitoring. It will stay put.
So don't let anyone charge you outrageous monthly "monitoring" fees under the guise that your rank can plummet if they aren't watching. It won't--not if the visitors to your site keep coming back for more and pointing their network of friends, family and business associates to you. Keep it active, keep it relevant, keep it helpful, and your page rank will take care of itself.