In a business the most important thing is to avoid losses and that too of the kind where you are cheated straight out of your money eg bad debts. So if a company is cautious doing business in a risky environment then we cannot blame that company for it.
Also Flipkart must be having lot of options on its hand regarding where to prioritize investment and simply UP seemed not worth to them right now. It happens all the time. Even sometimes Delhi or Mumbai get products or stores after launch in other parts of the country.
The official word from Flipkart was courier constraints. Please at least read up my previous posts. I have been parroting the same thing 'n' number of times here. The speculations were three:
1) People ordering COD and not honoring deliveries
Simply stop COD orders instead of putting a blanket ban on all orders (including prepayment orders)
2) Poor sales tax regime in UP
Does not explain how smaller players like Snapdeal are able to cope with it while bigger players like WS Retail are not. Also does not explain why the monetary limit was Rs 10,000 for Noida and Rs 5,000 for Meerut. Both fall in UP.
3) Credit card fraud
Anyone believing that widespread credit card frauds were being conducted from UP is only kidding himself. UP is no Nigeria.
Also, as Sushubh said, a simply credit rating of customers could have solved the issue.
As far as the last part of your statement is concerned, Flipkart may well stop business in half of India for all I care. Snapdeal and Amazon both deliver in my area without any restrictions. The issue here is retail monopoly. With increasing exclusive tie-ups and the retailer's disinterest in a particular region the day won't be far when ~20% of Indian population does not have access to various products. What then? Put smartphones under ESMA? Because like it or not, smartphones are the essential commodity of tomorrow. Your analogy of Delhi and Mumbai getting delayed products does not hold water because the issue here was non-availability of product and NOT delayed availability.
And so much for people of UP defrauding Flipkart. I wrote two long emails - one to Motorola and one to Flipkart pointing about the negative side of retail monopoly and voila!, there are no more restrictions on my pincode as of today. Probably they acted on my complain. Probably this is just coincidence. I would like to believe the former.