The Ignition Poker bonus of 100% up to $1,000 (150% up to $1,500 with Bitcoin) unlocks at a rate of $1 for every 30 Ignition miles you earn. You get 15 Miles per dollar in rake contributed or tourney fees paid, so this works out to an astounding 50% rakeback equivalent. You have 30 days to gather as many Miles as possible to clear your bonus funds.
The bonuses at Bodog.com and Bodog.eu work in a similar fashion, but Bovada has a slightly different bonus deal that's capped at a maximum of $500 instead of $1,000.