I really do not like it when bounty managers do not limit the number of participants. I believe that this is not right and not fair. Now a lot of people want to participate in the bounty. Often the bounty does not have a lot of money. I've had cases when I got less than 5 dollars for 20 weeks of TW&FB bounty. And such things will faster kill the bounty than anything else. 
Bounty managers will never limit number of participants. For what sane reasons they should decline project advertising's rise for the same costs?) I've seen one bounty that allowed even newbies as participants