Unclaimed prizes are kept by the lottery jurisdiction. If a Grand Prize goes unclaimed, the money must be returned to all lotteries in proportion to their sales for the draw run. The lotteries then distribute the money, based on their own jurisdiction's laws, to other lottery games or to their jurisdiction's general fund, or otherwise as required by law.
Despite the uneasiness of many to begin with, I know of no disputes or complaints from people who have bought Powerball tickets online via the insurance model, won and not been paid. As you can imagine, this scenario would effectively close down their website as they rely solely on the trust factor. The insurance model means that you will not be buying “official” tickets, but what do you care if you get paid your millions at the end of the day!
Before the agreement, the only places that sold both Mega Millions and Powerball tickets were retailers straddling a border; one retailer on the Sharon, Pennsylvania/Masury, Ohio border sold both Mega Millions (via the Ohio Lottery) and Powerball (Pennsylvania) before the agreement and continued to be the only retailer to sell tickets for both lotteries.
Bob Bolduc, founder of Pride Station & Stores, where the prize was actually purchased, said the multimillion-dollar winning ticket was sold at about 2:30 p.m. Wednesday. He said that in the past year the convenience store chain has sold a handful of winning tickets worth $1 million or more, and he suspects that will “resonate with a lot of lottery buyers.”
Mega Millions' second-largest jackpot, $648 million, was for the December 17, 2013 drawing. Two winning tickets, one each from California and Georgia, were sold. The holder of the Georgia ticket claimed the next morning; they selected the cash option, which amounted to $173,819,742.50 before withholdings. The holder of the California ticket claimed on January 3, 2014. (The California ticket holder received an equal share, but potentially a larger cash-option amount, as California lottery winnings are exempt from state income tax)." 
Giant Lottos offer Quick Pick, Manual, Syndicate and Bundle purchases on USA Mega Millions tickets. All you need to do is choose your preferred playing method, buy your USA Mega Millions tickets online, and our team will ensure your tickets are bought within the same hour. We at Giant Lottos strive to make you a millionaire as quickly as possible!
For a monthly fee, PlayEuroLotto syndicate betting can boost your chances of winning a serious lottery prize dramatically. In a syndicate betting, lottery players pool their lines for a draw and agree to share any prizes won. If any of those lines wins, then you get to share in the prize money. The more shares you bet with, the larger the share of the prize money you win. Acording to the UK National Lottery, 1 in 4 jackpots is won by a syndicate.
This method specifically has faced criticism recently from a number of lottery organizers such as Camelot, the UK National Lottery organizers who are not happy with companies “selling tickets” (selling bets on outcomes of their established lottery draws) for prices sometimes even cheaper than Camelot themselves sells their tickets. This legal and corporate dispute looks set to continue for the foreseeable future, in the mean time you can continue to buy Powerball tickets online, only now you are aware of the key differences between the two business models.