Verizon Wireless is no longer the presenting sponsor of the current Gwen Stefani Sweet Escape tour. Stefani can thank the trek's opening act, Akon, for Verizon's abrupt decision to sever its multi-platform ties to the tour.

Last month, during a concert in Trinidad, Akon danced provocatively with a 15-year-old fan. When footage of the onstage dance found its way online, Verizon got cold feet. (Akon's show in Trinidad was unrelated to and not part of the Sweet Escape tour, which commenced April 21 in Phoenix.)

William Chipps, senior editor of IEG Sponsorship Report, calls the action taken by Verizon extremely rare. But, he adds, there is always a risk involved when corporations sponsor a music tour or have an endorsement deal with a celebrity. "You can't control the actions of celebrities," he says.

Industry sources put the cash value of a tour sponsorship package--like the one between Stefani and Verizon--in the $1.5-$2 million range in cash, which artists typically use to finance production, startup costs and other tour expenses.

But marketing value can be worth as much as $1 million or more. Stefani manager Jim Guerinot, of Rebel Waltz, declined to discuss the financial terms, but does tell that "we're just in the beginning stages of evaluating" the impact of Verizon's move. Regarding the presenting sponsorship, Guerinot says, "We're surprised and shocked they've backed out of it."

As for Akon, Guerinot says, "Akon has been a perfect gentleman on this tour. His show has at best been a PG show. Children of all ages have been attending. We have had no complaints--nothing but satisfied people. And I would say that we're shocked that Verizon would drop Gwen Stefani as part of this whole debate."

Unfortunately, notes Chipps it will be difficult for Stefani and her team to pull another sponsor into the the Sweet Escape tour, as "these deals take months to put together."

In the long term, though, Chipps is confident that Stefani will not be affected by Akon's "inappropriate behavior." For Akon, it may be a different story. "A company will think twice about aligning with him," Chipps says. "Hopefully, Akon has learned a big lesson."

To this point, no dates have been cancelled and Akon remains on the tour.

Akon was unavailable for comment. Verizon was not immediately available for comment.