The problem I have is not with the biblical prosperity that is promised. The problem I have is with the RADICAL prosperity message that is espoused by some. For those, they preach the message not to make everyone else rich, but so THEY can be rich. They tell folks to sow into THEIR ministry because THEIR ministry is fertile soil. In all my years of pastoring (over 25) my observation is that the only ones who rich from the RADICAL prosperity message is those who preach it!
Don't get me wrong...the Lord has prospered me and my family abundantly. We freely and joyfully give and have given. I have NEVER EVER told someone to give to my minister because it it fertile soil and they will be blessed because of it.
I believe in prosperity. Prosperity comes from working diligently, using wisdom, being honest, liberal in giving, spending less than you make. It is more about Proverbs living than it is plopping some money down Mike Murdoch style and expecting someone running down the street to hand you an envelope full of money! (and I know God can do that) It's just that most of these guys sell their "formula" like the late night get rich quick schemers by using the small minority of those with incredible stories to tell everyone that they can have it too! I was born at night....but it wasn't last night!
I personally know at least one pastor who said that the prosperity gospel is where the money is! I think Piper is right on target in what he is coming against...the RADICAL prosperity preachers.
Like I said, I have given and been blessed because of it. But I don't give to get blessed. I give to be a blessing. If I want to make some money, I may make an investment. I don't give in the kingdom for an investment. I do it because it is the right thing to do. God IS concerned with out motives.