Tithing in today's church buildings' settings is part of their business organization. Building and maintaining the structures, the electricity, water, parking lots can only be kept up with money.
Before I forget, Newt Gingrich will be speaking at John Hagee's church "Cornerstone" in San Antonio, Tx at 6:30p. Get their early !!!!! 
There are tax write offs for the pastors of the church buildings. I believe (not positive though) even their homes, cars and traveling expenses are write offs. The congregation who tithes w/a check or credit card can also write off contributions on their taxes.
SO what if the govt. stepped up and decreed churches could no longer write off their contributions on taxes. (Rome for starters would be FURIOUS) followed by everyone else. The govt would not be saying a person could not tithe. It would simply be saying "No tax write offs for church contributions."
I think a lot of people would be sweating bullets and true FAITH would have to be put to work.
Personally, don't we true believers trust the Voice of God in our spirit? If He tells us to give, regardless to WHOM, we will obey. Why must we be told we MUST TITHE ! Do the puppet masters not have Faith in God to speak to us individually?
ALMOST ALWAYS, when a person buys a teaching, CD/DVD or product from a preacher/teacher, you will be put on a mailing list. You'll receive a nice packet from them with the latest teachings/products and an offering envelope.
In most mega churches, the tithe is different from an offering. In some services, there will be the tithe collection followed by 2-3 offerings. AND Always when a guest speaker comes, an offering will be taken for the speaker even though in most cases the speaker CHARGES a FEE for coming to speak to a "church". Their fees are NOT cheap either ! AND they must be picked up at the airport, be put up in a hotel in most cases and all at the expense of the invitee. That's all on top of the speaker's FEE !
In return, the speaker who in most cases is very well known will draw in the crowds and in many cases to standing room capacity only. The tithes/offerings will certainly be 'huge' that weekend. The speaker also lavishes his praises on the pastor who invited him/her to speak. This makes the congregation feel all "PROUD" of such a FINE man/woman of God. To the newcomers, they will be "WOWED!" by the speakers' comments on the pastor and thus possibly increasing the membership to that church, resulting in........ you guessed it: more $$$$$ for the church.
Let me also say, most big named church pastors have a payroll. They have a staff on salary working for them providing health care and 401k benefits as well in most cases. Many of the well known pastors make annual salaries in the MILLIONS. Their staff make good salaries too but must sign loyalty contracts.
I've been there.
That said, if the Holy Spirit leads you to GIVE, by all means Give ! Just be cautious and careful.