[jmgurgeh]

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My wife, a network admin, said that if someone were trying to change their mac address, then it was probably for some nefarious reason.

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In general I think she's right, even in terms of online poker. However, there ARE good reasons to want to change your MAC address (I'm assuming here that it's the MAC address that sites use to identify you, since most IPs are dynamic). Here are a couple of examples I know of first-hand.

1. My computer used to be the common family machine, and my brother signed up for Royal Vegas for the College Poker Championships (or whatever it's called). Months later, I wanted to sign up so I could play in it too, but they wouldn't let me register because one account had already registered from my computer. This was part of their grand "security plan" to prevent collusion.

2. After getting one of our friends to sign up for Eurobet (this guy's first online poker account), my brother made the mistake of using his own laptop to log in to this guy's account. He did so just to show him how to use the software and did not start playing. Nevertheless, my brother (who is usually at 5-10 or NL 100 tables) is not allowed to sit with his friend (a strictly $.50-$1 player) at the same table again. The rationale? They could be colluding. At $.50-$1.

So changing your MAC address really should be a shady thing to do, but since these sites have such retarded "security" policies that rely on badly written hard and fast rules, some people have legit reasons to change it.