bold emphasis mine
Not to call these posters out but if I heard these comments in my church I'd be tempted not to give there (and I work with finances for my church too). The God who created the world (without you sending in your piddly check) absolutely does NOT need our money to keep our churches going. God can raise up the poorest church and bankrupt the largest most giving church in seconds if He saw fit. The church does not depend on its members, it should depend on God. God does pay our heating bill by convicting people to give, or creating miracles because it all comes from God and belongs to God, no matter whose hands deliver it. I saw this with my own eyes, when my tiny church at my last home needed a bulding (rent was crazy expensive), but a chuch buying a property in Silicon Valley during the internet boom was UNHEARD of. The asking price for the property we got was over 5 million. We got them to GIVE it to us. We got a company to GIVE for no money a 5 million dollar property to a church in Silicon Valley during the dotcom boom when properties were selling at least 20% OVER asking. They even paid closing costs. Can you imagine having the balls to even call in and present that offer (um we'll pay you nothing and you'll take it) but they felt God was telling them to ask for that property. If that isn't God providing for His church I don't know what is.
Tithing isn't about paying for things God can't pay for, its about showing God (in a way that is honestly a little painful... who doesn't want to hold onto their money), that He is first and that we recognize that everything we have comes from Him and thank Him for that by giving back to him. It helps us keep our priorities straight, and allows him to show us the ways he can bless us when we do.
I really struggled with this recently at my church. Another start up small church without a building (we have a small office building and meet at an elementary school). I felt I was being called to give my money to a cause in Kenya, that God has really placed on my heart (was there in July and will be back next month). However (because I work with the incoming finances) I knew we were one of the largest regular givers at our church and that our church would really hurt without the money. I prayed about it and felt God ask me why I was being unfaithful, why I was holding onto the concept that it was my money that was doing these things and not Him. I began sending my tithing to the cause in Africa, stopping at my church and when i did tithing at my home church immediately rose up and covered what we had been giving (and no one knew we had decided to do this). God took care of my church still and used the experience to remind me that these things come from Him, not me.
BTW, back on topic, none of the churches I have chose to attend as an adult (non-denominational, fully Bible based) have ever sent out letters, besides the one the government requires to prove how much tithing you gave for tax deduction purposes.