The 1N4148 is very inexpensive and works well to cover a lot of low current applications. You are correct that they are quite common. I salvage a lot of circuit boards and it is rare for there not to be at least one and frequently 10 or 20 on a single circuit board. There is also several manufacturers who have made this device under the same part number. Occasionally there will be a slightly different first 2 characters in place of the 1N but the 4148 remains the same. Because of this the parts has been used in boards from all over the world. Even Wikipedia has an article about it.
1N4148 is an incredibly fast responding diode. The recovery time is around 4ns. Which means it can come out of conducting state to blocking state in 4ns. If you consider the 1n4001 another commonly used diode the recovery time is around 2uS.
Which is around 500 times slower than the 1N4148. I generally use 1N4148 diodes for analog frontend protection circuits. If you want to protect a differential amplifier from a sudden transient voltage you can use 1n4148.
