One of the biggest arguments is that it is a 'copy' of the original and it can not technically be called theft.
Theft: The wrongful taking of the property of another. It is a broad term and includes larceny, pilfering, hold-up, robbery and pick-pocketing.
With theft being defined as 'taking property' people get the idea that copies are not property, which is incorrect. The definition of property does not limit it to physical items
Property: In legal terms, property defines anything that can be owned: either an object or a right.
A company owns the property rights to all of their software, and are free to enforce it how they wish. If they do not want it 'freely distributed' they have the right to prosecute anyone that has violated their rights as they feel fit. Most software companies include a TOA (Terms of Agreement) or EULA (End Users License Agreement) that they force the user to read before installing the software, this is the part that most people hit "I Accept" and continue without reading a single word of the agreement. Within this agreement is usually their 'acceptable use policy' which may go into detail on making copies and how openly the software can be distributed. Normally this includes an install on a single machine and the ability to make 'backup copies' of the software. Many times they specifically state that the software can not be 'passed along', installed on more then one machine or copies made for distribution. A copy includes ISO data images and/or physical copies of the media.
When it comes to the use of P2P networks, most people feel that it is acceptable to download software off of these and use them as they feel. Many times the defense to such actions is that they are using it "on a trail bases" and will remove it and purchase the actual product if they "feel" that it is worth it. Even if this is true, it is still using stolen property. Justifying it by saying that the retail product will be purchased is on the lines of me saying "I'm just borrowing your girlfriend, if I find that she is worth having I'll go get my own...don't worry, she's still yours"
I didn't 'steal' your girlfriend, I just wanted to 'try' her.
Most software offers a trial copy of their products just for this reason, so a customer can use it to see if it meets the customers needs. True, many times these trials are 'crippled' with features removed disallowing full use of the software. This is done to 'persuade' the customer to purchase the full product so the customer does not get by with using a trail version forever. That is also detoured by the use of 'trial periods', but in these cases the software is nearly fully functional and the customer can get a full feel of what they are going to get.
Sometimes a company will not even have demos or trial versions for testing, IMO they probably do not have a product worth purchasing if they have to hide it. Find an alternative.
There are many opinions (which this is one of) and arguments on this subject, I would like for you to post a comment, complaint or troll on this entry about Software Piracy and Illegal Copying of Property.