The Wall Street Journal published an article today on How Search-Engine Rules
Cause Sites to Go Missing suggesting Companies that make a change to their domain name, usually legitimately, don't get enough of the right kind help from Search Engines, even when they ask for the help directly and are willing to pay for it.

"…Further frustrating him is that Google's response to Topix's plea for help was an email recommending that, if the switchover were to go badly, the company should post a message on an online user-support forum; a Google engineer might come along to help out. "This can't be the process," Mr. Skrenta says. "You're cast into this amusing, Kafkaesque world to run your business."

He's among a growing group of businesspeople whose fortunes are buffeted or burnished by the invisible, constantly evolving mathematical formulas at the heart of Web search engines. The influence of search engines has only grown in recent years, as they have become the de facto gateways for many of the more than 180 million American Internet users to anything they might do online. They also have become a crucial tool for businesses that depend on those users finding them."

Now that Search Engines have become so mainstreamed and a vital source of traffic to  sites - it seems reasonable for a legitimate business to ask for help, especially if they're willing to pay for it, to ensure that the new domain does not fall out of the Search Index(es).

But the Engines haven't caught up - no one seems to see it as their job to make sure sites that make legitimate changes stay in the search index and don't lose the positioning they worked on achieving.

That's because Google does not want sites to depend on Search Traffic for their business success….yet, paradoxically, the reason why Google is so successful is that it sends a lot of traffic to many sites that are now crucial for success.

"…Google, of Mountain View, Calif., says it offers online tools for companies to get the best, most consistent, treatment from its search engine. It also counsels that sites shouldn't become overly reliant on traffic from searches and should find other ways to get visitors, such as by setting up user forums. "We have to keep improving our algorithms and giving the best search results," says Google software engineer Matt Cutts. "We can't promise that if you're No. 1 today, you'll be No. 1 tomorrow."

It does seem like Search Engines should do more in situations like the one Topix.net / Topix.com is in:

"…Even if traffic to Topix, which gets about 10 million visitors a month, dropped just 10%, that would essentially be a 10% loss in ad revenue, Mr. Skrenta says. "Because of this little mechanical issue, it could be a catastrophe for us," he says."

The problem has to do with redirects and having Google discover, crawl and rank a new domain - it's a non trivial effort and newer webmaster tools do help (Webmaster Central) but doesn't go far enough.  I think Google, in a case like this, needs to facilitate and monitor the entire process - if the company is willing to pay a reasonable sum for it (I'm sure they'd be happy to pay to be sure they're not dropped or lose rankings over a domain name change).