It's a common practice about as old as the wrestling business itself. When a wrestler moves from one of the smaller, independent, territorial promotions to the "big leagues" (which today would be the WWE or TNA), he/she may have to take a new ring name and/or persona to avoid having his/her real name or previous, self-created ring name trademarked by his/her new employer. The "major leagues" want to create merchandise for as many of their performers as possible, to better sell said performer to the public at large. While this is all well and good, not all wrestlers are willing to "sell out" their identities.
Let me give you one good example. Sid Vicious was well established in the southeast before signing with WCW in 1989-90. Sid, of course, can also be credited with helping Booker T get his big break when he convinced WCW to sign Booker and his brother Stevie Ray, collectively Harlem Heat. However, when Sid jumped to the then-World Wrestling Federation, his name was changed to Sid Justice upon his arrival in the fall of 1991. It changed again a few years later during his 2nd and final tour, to Sycho (yes, that's how it was spelled by the grammatically challenged creative staff of the period) Sid. Sid Eudy had already trademarked "Sid Vicious", since the rock musician who used the same name was already long gone. I would assume he had a deal with WCW where he could keep the name, but Vince McMahon wasn't willing to broker a similar deal. Of course, the rest is history.
Fast forward to today. Johnny Stamboli had developed a new ring persona, dubbed Redrum (Murder spelled backwards). WWE gave him a look, then passed. He has since signed with TNA, but rather than sell the name Redrum to the promotion, Stamboli compromised, and the result is Rellik (Killer, natch). Senshi (Low Ki) had made the same compromise about a year or so ago. Meanwhile, two of TNA's newest "Knockouts" had their names changed by the marketing department at last week's tapings.
Talia Madison, girlfriend of WWE star Gregory Helms, will be using the name Velvet Sky when she appears on Impact this week. Similarly, Angel Williams is now known as Angelina Love. Neither woman was willing to put a trademark next to their names, so the creative team created new identities, this despite the fact that Madison & Williams had already appeared on Impact. In this case, TNA Uncreative was a day late and a few dollars short. Now, they're trying to make up the loss, but is it at the risk of two developing careers?
By virtue of saving their own names, Madison & Williams can continue to use them when working for smaller promotions. By that same token, Senshi & Rellik can use the alternate names when not working for TNA. In the long run, it's smart business where everyone benefits.