A close personal friend of mine was screwed over by fum.us. I feel responsible because I referred them to the service after reading good reports of it on here. You can choose whether to use this service. It your choice, of course. But I'll tell you what happened to my friend.
They created an account and purchased $10 worth of credits. Only a small amount, granted, but still hard earned money. They stipulated U.S traffic only in the campaign. It soon became clear fum.us could not provide enough US traffic because they changed the source to include other countries. My friend didn't like this because they only get paid on US traffic for this campaign. They complains. The next thing they know their account has been deleted and no traffic has been sent.
Use FUM.us at your peril, especially if you want US traffic. My friend only lost $10 but I'm reporting about it here because I know some of you high-rollers stand to lose hundreds or thousands of dollars.
KK