There are many kinds of lies, across a broad spectrum and on multiple axes. Some lies are easier to tell, some are easier to make up, some are easier to excuse, some hurt others less, or even help. There are white lies; lies you tell because they won't hurt anyone, might help someone, and don't seem very bad at the time. There are small lies, which you deem worthwhile enough to make even though they might have negative repercussions. There are exaggerations and hyperbole and stories that grow in the telling or for effect. There are big lies, which might be selfish or profiteering or malicious or evil, the sorts of lies that ruin lives and make fortunes. There are butler lies, excuses to get out of conversations or situations. There are lies of omission, leaving out details to mislead someone "without lying". There are combinations of all of these, and gradients between them.
Our culture seems to be on a long slow path of lying becoming more common, acceptable, or excusable. The is more unfortunate than it might sound because it's not consistent. What to one person is a small white lie is to another person a big lie. Even if both parties have all of the relevant information they could classify the lie differently. It's rare that all the information is available so it's likely that an individuals classification of their own lie is also inaccurate even by their own standards. They choose to tell it because it seems small, but if they knew the impact it would have or the real situation then they wouldn't. Hyperbolic lies tend to grow, especially when the re-teller of the story knows the original story was a lie to begin with, mimicking a game of "telephone" where the originator might not even recognize the tale when it returns to them.
Perhaps I am mistaken about lying becoming more common. Perhaps it has always been just as acceptable as it is now, but modern technology allows us to uncover more lies so we see what appears to be more lies being told when the number has really not increased. The internet and the sorts of accountability and rapid communication that it brings means that more lies can be uncovered more quickly than ever before. Unfortunately I would be naive to expect this to lead to more honesty instead of simply illustrating the already-existing levels of dishonesty. It remains to be seen whether my naivete in trying to convince people to lie less often will be detrimental for me in the long run.
I am writing this because I, just today, called someone a liar. I've a mind to repeat the accusation more often against others in similar situations. They are occasionally people with a modicum of authority over me in a social environment, and whose wrath I do not risk lightly, but I have come to a breaking point on this issue. I make true accusations and they are defended against falsely and I will not stand for that. The specific accusations are usually of such small importance that they are virtually irrelevant when put next to the lies being told to escape them.
 "Liar" is very strong. "That's a lie" is less so, and "That's not true and you know it" less so still. They all mean the same thing, but are interpreted different ways.
 specifically American, around 5th-95th percentile income individuals and families.
If you don't want to talk to me, tell me that you don't want to talk to me, don't tell me your dog is on fire. If you don't want me to talk about a certain subject to you, or with other people, tell me that, don't lie to me in an attempt to convince me that talking about it isn't worthwhile. Lying to me is almost never going to have the desired result, and the more effectively I can convey that the more likely we are to have successful communicative interactions.