Yup, the same suspects win time and time again.... because they buy so many tickets. They're addicted, it's fairly simple. I have also won a lot of good basses on various sites, mainly Guitar Gear Giveaway. The last one I won was last month, an EBMM Stingray (3EQ) in translucent orange. Prior to that I've had another Stingray (2EQ), a 3rd Stingray, a Rickenbacker 4003, Fender: American Jazz, Mexican Jazz, Aerodyne Jazz & a Telecaster, an Ibanez SR300, a couple of Squiers and an Epiphone SG.
For a couple of the above list I have collected them rather than having them delivered, so I've personally met the guys that run both Guitar Gear Giveaway and BassBros competitions, they're all thoroughly decent folks. And yes, they do try to sell around twice the instrument's worth in tickets, but they don't always sell all of the tickets before they're drawn - but they're true to their word in that they don't extend the 'competition' (raffle!), even if they're making a loss. They also have overheads to meet as well as paying themselves a decent wage, so I don't think what they're doing is unreasonable. The draws are done live on YouTube/Facebook/whatever, using google's random number generator - they're as open and honest as could be about it. I wouldn't be entering these draws if even thought there was a possibility they weren't on the level.