By sampling other people`s work without agreement from whoever owns the copyright to the original work (that is whoever wrote the original or who now owns it if it has been sold on) and whoever owns the performance rights is illegal and you would therefore be open to prosecution for breaking the law.
In the UK most rights are registered with the MCPS (Mechanical and Copyright Protection Services) and the PRS (Performing Rights Society). Each country has its own method of protection - for example in Italy it is the SIAE.
If you are sampling with no profit you will still have broken the law.
Would you get away with it?
Depends who and what you sample and what you do with it and whether the MCPS or PRS or the people who wrote and produced the original find out and then decide to do something about it.
Sample some huge well known artist and you stand a bigger chance of getting caught.
Sample some obsure italian acapella and the chances are you would get away with it.
If you had not made a profit it is likely there would be no claim for compensation - if you did make money they would certainly want all or part of it - as in the Snap case. That title made a lot of dosh and now they want their fair slice.
Another example was the use of a Madonna sample in the Mad Angels track We Can Make It Alright - the release had to be pulled by DDM (and is the reason it is quite rare btw).
Slightly more extreme example is The Verve`s Bittersweet Symphony where the famous string hook was sampled from some obscure album of orchestral interpretations of Rolling Stones tunes by Andrew Loog Oldham.
The deal was that they took ALL the copyright royalties from the song.
Rolling Stones' manager derides The Verve | News | NME.COM
Where there is money to be had increases the chance of the owners doing something about it to get their share.
