You could buy a cart full of stuff for just the price of a soda, if someone hacks the software on the phone. You wish.
They already have self check out lanes that are always manned with security detail. They will most definately be checking reciepts.
Walmart want to get rid of cashiers eventually. The current self checkout can pretty much do anyhing a human cashier can do but does not need to be paid an hourly wage of $7.25, does not need breaks, will not make mistakes, will not give bad customer service. The iphone and eventually android checkout apps will be a step in the direction of eliminating human cashiers to increase profitability.
You are right that it does not need an hourly wage, doesn't need breaks, and doesn't need benefits and in general is cheaper than a human wage slave.
But... it still does have some maintenance costs and while it may not make mistakes it also is easier for people to find ways around to steal, and bad customer service? It won't be giving good customer service either. Just cause it doesn't insult people or have a bad mood doesn't make it good customer service (That's just minimal customer service). For many people, even those tech inclined (but less so), they'll find they wish they had a real person (that isn't limited to set answers, that is willing to actually show you where something is, that can actually have the power to override a rule if they feel it warrants it <- in fact you get better customer service at stores that allow their employees some leeway in how they enforce rules rather than the ones that are very strict on their employees that they cannot bend rules or have to always get a manager to do so).
So, it's cheaper and for a place like Walmart probably for their bottom line it is better. But if a store wants to be known for good customer service (one of the few ways to still compete with Walmart and even online stores), they really still do need people.
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You make it sound like people at Walmart are forced to work there. If they don't like the wage they are paid, or benefits, or lack thereof, nothing is stopping them from getting a job elsewhere.
In places where Walmart has succeeded in chasing off the competition the fact there is nowhere else is stopping them from getting a job elsewhere. Or for that matter most places around the country jobs are not that plentiful right now (and retail really is hurting. Not just from walmart but from online sales) so telling some one to go find a job elsewhere is really ignorant. Most retail is not hiring full time anymore and tends to be understaffed. I mean this whole thread is about how Walmart is trying to reduce the amount of people they hire...
It's really easy to say, "don't like it, go somewhere else". A lot harder when you are in that position. Also, especially when people espouse that attitude that it is fine for a store to treat their employees how they like, what happens when the other places also do that because, well, it is cheaper... where do you expect the person to find another job that is any different? Retail, especially these days, is easy to find some one to fill a job. So why would other jobs feel any impetus to be any different? They don't need to compete to find employees.
Sometimes it does take an outer entity (Customer outrage on how they are treating employees or even government) if you really want to convince a place to treat the employees better. Cause the employees themselves don't have the kind of leverage to convince employers in that field to do any better and employers know it. This is also why Unions are not out of date. Sure, there are Unions who have gone too far and some fields need Unions a far lot less than other fields. But fields where there is not much skill needed and anyone physically capable can do it are in need of it far more. There was just an article recently about a coal mine that was not unionized that forced their employees to go and donate to a political event. The owner said, "We had managers that communicated to our work force that the attendance at the xxxxx event was mandatory, but no one was forced to attend the event." Are you going to tell those people that if they don't like it they can find a job somewhere else when that is the only job that is available in that area? Your attitude seems very similar to the manager, "Oh, they can just find a job elsewhere if they don't like it." Difference is that manager knows very well that there is no elsewhere in that area (at least you can say you didn't think about that).