Hello 'jg01302',
What does it block out? Well, what you most certainly suspect, - shillers bidding up their own items.
That may not be what is happening, as some sellers list all their auctions that way and let the
auctions run their natural course. If the item only fetches 99 cents, so be it.
Some items should be private, whether auctions or fixed price, -- like foundation garments, that sort
of thing.
If you have read the link 'toby' provided, you have seen where it instructs sellers, "you should only
make your listing private if you have a specific reason".
And yes, that specific reason may be to mask the fact that the seller is shilling. It happens quite a bit.
Sellers are not supposed to do it, and in some countries it is even illegal, but don't expect to ever see
anything come along to stop it.
If it bothers you, don't bid on the item. The best cure for a shiller is no bids at all. (It's obviously not
a high bid at the end, as many shillers place their bid on their item and wait for the snipers to overtake it).
Otherwise, if you like the item and want it at a reasonable price, bid what you are happy and comfortable paying,
bid as late as possible, and if you get the item, -- it's the same as if you bought it elsewhere for a fair price.
Whatever you do, avoid that nibble bidding, where you let the shiller work your max bid up a little at a time.
That's why so many people like 'sniping', - that sneak-attack bid at the end. It prevents others fiddling your
bids up, . . . and it's fun.
You will have seen this info page about about ebay's automatic bidding system:
http://pages.ebay.ca/help/buy/automatic-bidding.html
And if you want to peruse ebay's official policy about shilling,
http://pages.ebay.ca/help/policies/seller-shill-bidding.html
but as anyone who does much bidding and buying will tell you, it's only there to cover ebay from a legal
perspective, -- nothing is ever done about it.
Just use your common sense when buying online, and if you find something that makes you uncomfortable,
move on.
Happy shopping 
