The obvious ones are:
Unable to read properly
Unable to write
But how about funny noises created by the drive (If Drive still burn and read as normal)??

The answer to your question is, "It depends almost entirely on the company/person who is handling your RMA request." Some retail chain stores are very good at this, WalMart comes to mind as one example. If you bought mail order, then it varies all over the place. NewEgg is good. Call or send email and ask, you have nothing to lose.

For example, u have used a drive for 10 months then it start having weird sound coming from it buy burn OK, can u RMA it??

Hard to say. Maybe first check what / how much they will charge you for sending something in though it is not necessary, and whether this sound may be an indicator of oncoming drive failure.

Keep in mind RMA / Warranty policies differ from country to country. There is no standard practice. As HenryNettles said, it also varies according to the very person you are talking to. That is why it is often important to record the name of the service person you talked to and exactly what job title that person had at the time of conversation. In South Korea, services are exceptionally good and easy but South Korean consumers pay 2 times the export price. Whether you want to pay double to have a little better services is often at issue. Personally, I'd rather have a DVD writer or a HDTV at 1/3 or 2/3 prices from the regular ones without any kind of warranty. Failure rate is usually close to zero and by the time an electronics hardware wears out, I'll have far more updated replacements.

BTW, after my daughter did something, my PCH-S2300 camera phone and Gen Networks DivX player can't be played on TV. I don't know whether the cables have gone wrong or whether some boards failed. What I do know is they both went out of order right after she did something to them. I can either send the phone to Samsung service center or visit one myself. I can also send the DivX player to Gen Networks HQ in Seoul, or send it by mail service or anything else. Either way, it doesn't take more than a few days to get replacements or make them fixed and have them back. But if it's just the cables, it's easier and faster to order new cables from Samsung and Gen Networks.

I agreed with u Kenshin, half the price without warrenty is worth the risk however 1 month warrenty would be good, or am i just been plain greedy :P ?

Hardware failure rate is usually under 1% for big ODD manufacturers. Let's say if I buy 100 drives at once. The likelihood of at least one of them fails inside 2 years after purchase is not high.

What I mean is that warranty is just reflected in the retail price. Excessive warranty just means added cost. There are more than one distributor of LG GSA-4163B drive in South Korea now. There is LG Electronics. There is "Joeun Tech", a small company that imports and sells LG, Pioneer, and other drives. There is GnGear, a company which uses Headerway's service center in Seoul which specializes in Pioneer and 4KUS drives. And still at least one more. Those companies all apply different warranty policies. Since warranty practices are often affected by the very people who actually meet and talk to customers, training and personality of service personnel are very important. Some employees are clearly more knowledgeable than the rest. Some of the service center people readily give out shiny new drives to customers without asking too much. Some others first test and ask. Still others just don't do good works but blame customers when in fact the products are faulty. Thus it's very important to buy products distributed by companies that you are familiar with. Some companies have multiple service centers. Sometimes CEO's directly take charge and make things easier for customers.

Yeah thats what Gauss says and that Bullweiss distribution or whatever it was called...

BenQ owners made other experiences ... not 1%=0.01 but more like 1=100% In recent times there appears no one who has not RMAd his drive at least once or even more often.

2 years of warranty are required in Germany. Of course, maker often only offers one and dealer has to take the risk of the second... small dealer out of business, drive defective after 1 year? Bad luck!

How much does a LG 4163 cost there??OEM, retail, bulk?

Quick look:

Cheapest bulk (mail order) ca 57 EUR
Retail (also mail order) ca 64 EUR
Shipping add something between 4 and 7, dont know.

I think that shop has a good reputation. It may be possible to find the drive even cheaper. When you add shipping costs, you can go to a local shop as well and get the drive there for around 70 EUR as Retail (which is what I did, payed 69 at a rather big pc store which will for sure not be outta business anytime soon).

After my recent BenQ experience, I will buy at a local store again the next time I need such a thing. Sending in and waiting for replacement is annoying while going to the shop and come out with a new device in some minutes is much more satisfying.