I had to burst some of the bubbles about Las Vegas. But a host doesn't have a client list tucked away in some folder somewhere that he can just pick up and take somewhere else. It's 2011, not 1958.
Casinos, like all multi-billion dollar operations use several pieces of software to analyze their existing and potential customers. And based on that analysis, offers are generated.
Every person who signs up for a players card and tracks their play gets assigned a value. In general the value is based on hands played X number of hands per hour. The more you play the higher your value. Then based on that value offers are sent out. So let's say your value was 50. There is an offer generated for all 50s. You get the offer. Then one day someone in corporate marketing decides that offer is too generous for someone who is a 50 and sets the limit to only 55s and above. So you stop receiving the offer.
The value of each player is a little more fine tuned than just play. It takes into account hundreds of factors including age, marital status, kids/no kids, where you live, what kind of wine you like. And at any given time there are hundreds of active offers available. And it's that matrix of data that is used to generate targeted offers to individuals. It often seems random to the end customer, but there is a method to the madness.
Each casino has its own formula. And each formula is constantly fine tuned based on new information. And each casino probably has the same people in their respective database. Only difference is how much info on each person does each casino have. A host leaving Venetian could in theory provide some of that info to Wynn. But unless he does a full data data dump from the database, that info won't mean much to anyone. And even a data dump will be useless since the databases are normalized. So a host will see Joe Smith, 100 Main St, $100 /hand, blackjack, 20 hands/hour. But a data dumb he could theoretically take to Wynn would show Jack Smith, 2,4,2,6,2.
If there would be any kind of data theft it would be through good old fashioned hacking into a competitor's systems. Not a casino host stealing the data.