Like many people I am bothered by the concept of selling one's 
chametz.
Don't get me wrong, I 
DO sell my 
chametz, and although we try to finish as much 
chametz as possible before 
Pessach, to destroy what we don't manage to eat would be 
Ba'al Tashchit.
This year I learned that here in 
Modi'in the local 
Rabbanut conducts its own sale, instead of selling through the Chief 
Rabbanut which is done in many other cities. This made feel somewhat better as it is someone I know (Rabbi 
Lau) organizing the sale on a smaller scale than the 
Rabbanut HaRashit, which somehow makes it feel more "real" to me.
My biggest problem with selling 
Chametz is that for many people the whole thing is a farce or a source of 
ridicule, and worse there are people who may sign a sale of 
chametz form, but do not regard their produce as sold - what is the status of such produce? Is the sale still valid even if the seller shows that he still regards the produce as his? Does the 
chametz have the status of "
Chametz Sheavar Alav Pessach"
What if a store 
selles the same 
Chametz more than once (have you ever seen a store with a 
Tudat Mechirat Chametz from both the 
Rabbanut and the 
Badatz), surely this indicates that the store keeper didn't take at least one of the sales seriously.
Or take for example the following common 
scenerio in Israel:
Before 
Pessach a store sells its 
chametz and covers all 
chmetz shelves with plastic or paper, yet some customers (either deliberately or 
accidentally) reach behind the paper and place 
chmetz products in their basket.
At checkout, the worker may or may not know that the products are 
chametz, but one way or another the product is scanned and paid for by the customer.
As far as I can tell one of 2 things have happened:
Either the store never took the sale seriously, only sold the documents to keep those Rabbis happy, and it's hard to argue that there ever was an effective 
Mechirat Chamtz.
If this is the case, I don't understand how it could be 
permissible to buy any 
Chametz products from that store after 
Pessach.
Alternatively, the store really regards that the produce belongs to the non-Jew, but is selling products that do not belong to them.
In this case, isn't the store keeper a thief - stealing 
chametz from a non-Jew and selling it for profit without even notifying the owner of the produce. Why would you want to do any business with such a person?
If you think that there is 
another way to interpret the 
scenario of a store selling 
Chametz that it already "sold", please leave a comment.
Anyway, the good news is that according to the 
Jerusalem Post, this year for the first time the 
Rabbanut is providing all stores that sold their 
chametz a special add-on to their scanner which will prevent 
Chametz products from being sold.
It's worth reading the article at the Jerusalem Post Site, just to see the comments; however if you have the Jerusalem Post site blocked on your computer (which makes you smarter than me), here is the article:
Rabbinate first: Pessah barcode blockers
Apr. 2, 2009
JPost.com Staff , THE JERUSALEM POST
The Chief Rabbinate has harnessed the power of technology in its battle against hametz (bread and other leavened goods) this Pessah and will distribute special "barcode blocker" devices to stores for the duration of the holiday at its own expense.
The devices will contain a list of all the barcodes linked with hametz products and will not allow automated cash registers to sell those items during the holiday.
The Rabbinate gave food sellers until Thursday afternoon to either agree to install the barcode blockers or temporarily lose their kashrut certification.
"Selling hametz can't become a farce [on Pessah]," Ashkenazi Chief Rabbi Yona Metzger told Army Radio.
If buyers are not told that they may be buying hametz, the businesses will have their certifications revoked for the duration of the holiday.
Buyers who do not keep kosher for Pessah object to the Rabbinate's policy.
"It's a bit annoying when they take over your supermarket in central Tel Aviv," an angry customer told Army Radio.
In the past, people could buy hametz from stores who declare that their business is kosher for Pessah, with leavened items separated from kosher-for-Pessah products simply by the shelves being covered by nylon sheets.
"You just reach out your hand and take stuff from under the nylons," a customer said. "The supermarket doesn't really take products off the shelves - so I just took something, paid for it and there you have it."
The Rami Levi supermarket network has already decided to acquiesce to the Rabbinate's demand; the AM:PM and Mega chains said they were adhering to Pessah kashrut laws in any case and the Supersol network said it maintained good relations with the Health Ministry all yearlong.
This article can also be read at http://www.jpost.com /servlet/Satellite?cid=1238562890657&pagename=JPArticle%2FShowFull