What did disposable razor blades replace?
The straight razor.
Yes. Razor-Type Blades - such as box cutters, utility knives, and safety razor blades are prohibited BUT (disposable razors and their cartridges are permitted) This was right at the time of writing and based on US regulations. Other transport and security agencies may have different rules. For the latest information from the TSA, see the link below.
If it's a razor for shaving then yes. Answer: Using American Airlines list of restricted items, fixed cartride disposable or safety razors are allowed in carryon luggage, straight razors are not. Razor blades for safety razors (not cartridge blades for razors) might fall under the general prohibition of "Metal knives (of any length or type), box cutters, ice picks, straight razors"
According to the TSA website on what is permitted in carry-on baggage, you can bring "safety razors - including disposable razors." See http://www.tsa.gov/travelers/airtravel/prohibited/permitted-prohibited-items.shtm#2 . This would not likely include those old-fashioned straight razors that utilize disposable blades, as it is obvious how those can be used as a dangerous weapon. no
since the economy is controlled by the government, the government controls the number of razor blades produced. razor blades aren't a priority for the government making the number produced very small. this is similar to the previous communist economy of russia. they only produced small amounts of luxury items making them very difficult to obtain.and everyone is cutting themselves.