They need to be aware that they will likely lose their rankings. They'll want to reevaluate the value of switching domains like this..
Alright so I'm going to try this again. Without singling anyone in particular out, someone here is the exact opposite of right, which is wrong.
SEO and Local SEO are two completely different systems. SEO's that use standard SEO methods for ranking local businesses get "juice" and they may rank well in the organic listings, like any other business. And some of that juice "rubs off" and the same business may rank well in the Local listings also. But just because standard SEO methods (blog comments, forum profile links, web 2.0, link pyramids, etc...) "work" on getting the business ranked well, that doesn't mean that the SEO has done "Local SEO". They've set-up a spammy, fragile and unnatural looking profile that like a house of cards will collapse if the least little thing goes wrong.
In this one customer's case, the thing that went wrong was that his 35,000 backlinks fell to about 100, due to an algorithm update or whatever. You could see the sudden drop-off in Majestic SEO's report. One day he was "B" in the Local search results and had 35,000 backlinks, and the next day he was on page 3, and he had 100 backlinks. And his phone was dead, dead, dead at the very start of his busiest time of year.
What MIGHT have saved this guy is if he had a strong Local presence. When his backlinks took a dump, he had nothing but a well-done Google Places listing with an inaccurate physical address, and a website that didn't even HAVE his physical address on it. Of the 50 or so local citations he might have had, about 10 of them showed his business at 4 different addresses, 2 different phone numbers and under 3 different business names with about 6 different spellings.
So, when his "SEO guru" changed his Google Places listing so that the address was CORRECT, it didn't jibe with all the other local citations that said he was somewhere else. So Google concludes that, instead of being a Local Business with 100 backlinks (which is pretty good, for a local business), instead this guy was a non-local business with weak organic presence, with only 100 spammy backlinks, a few of which gave conflicting local addresses. A nothing. A nobody. At that's exactly where Google put him, which is nowhere.
So, when all these "SEO gurus" start yapping about PR, etc... none of that means squat because that shit can disappear the next time Google farts. But if you have a strong Local profile in place, Google will always believe that you are a real local business, with a brick & mortar location, and you service your customers on site (or not, but you want to hide that if it's the case), etc... Google has a completely different definition of the word "relevance" for local listings, and any "SEO guru" that doesn't have that as his 1st operating perspective has no business giving advice on what a local business should do.
And another thing the non-Local SEO gurus don't mention is that website traffic is not the end-all be all of Local business. They see things in terms of big numbers, and percentages of conversions and most of their gross income is profit. They think 1000 visits converting at 3% for $10.00 is "normal" and if traffic drops to 500 (X 3%) well that means they are making less money today. Oh well.
A local business might get 30 visits in a month, and convert 5 of them, and those 5 might represent 50% or 75% of their gross income. And from that they pay rent, electricity, phone, internet, webhosting, insurance, wages, SSI, taxes, etc... and if they are lucky they have something left over at the end of the month that's called "profit". You never hear SEO gurus talking about profit because they haven't got hardly any overhead, it's ALL fucking profit.
And so, they apply the square peg of their unique little corner of the universe to the round hole of what reality looks like, and when the small business's traffic drops to 15 in a month, and they convert only 2 of them, they can't afford rent, or electricity, or both. It's not just a minor drop in income that can be recovered over the long term. It's a BIG FUCKING DEAL, and it may mean the difference between staying in business or not.
So my point is, some of these guys throw around their big-city, SEO guru advice around without any consideration for the consequences to the small business owner if they are wrong. And I'm telling anyone that cares to listen, they are wrong.