I started referring to the act of loading an executable into working memory as an "install" after hearing Marvin Minsky refer to it that way during a lecture in 1977. Back then, we didn't differentiate between the act of "installing" in your sense (i.e. on a drive or other storage media) and loading it into RAM for execution. It was the act of loading and running that constituted the "install."
-40hz
If we're going back *that* far, then at that point there wasn't really anything that even resembles installations of today, especially given the change in media and storage technology, so I think that given the change in the English language and technology, to carry over a term from that time to apply to the methodologies of today is a pretty big stretch...
And since we're trotting out our CVs, my view is from the perspective of someone who (like yourself) has programmed and installed software on various OSs for...well, let's just say a bit more than several years, starting with IBM's System/360 on mainframes, and Digital Research's CP/M on personal computers. 
-40hz
I'd guess a bit more than several years would depend on what the definition of several years is.

For one thing, installation by any practical definition implies that the software in question can be run again without any need for further installation (leaving out the situation of a software upgrade, since the act of upgrading is changing the delta of the installed software.
That's a new one for me. Bounced it off a couple of system admin cohorts of mine. Both felt your qualification that it "can be run again without any need for further installation" is not a valid criteria because they routinely install and run software utilities (not updates) that execute once and then remove themselves from the system. 
-40hz
Personally, I wouldn't consider that an installation any more than I would consider copying a file to your computer or executing said file from a usb drive an installation. /me shrugs
But I think that with that out of the way, i.e. you've defined what you refer to as installation as anything that runs on your computer, then that seems to erode your position even more (see arguments by renegade and f0dder)

It seems like there is a lot of getting hung up on terminology here. Which is ironic because one of the most important points made here - by 40hz - is that the meaning of words *is* important and is being potentially subverted here by OC. On that point I have some concern myself. Nonetheless I think whether something is "installed" or not is ultimately tangential to what is at issue here and of actual concern. After all, I'm sure Wraith would not argue that a virus that simply loads itself into memory and formats your hard drive without ever "installing" anything is ok simply because it's not being "installed" (and neither would anyone else I'd wager
). So using "installed" as a measure of trustworthiness, safety, or anything else that is really of concern here is not really useful.
-JavaJones
First, installation was brought up by the nay sayers, not me. It was in their own words that the problem with OC was that it installed without their knowledge.
Second it is the words that are my
entire point of this conversation. OC is *not* adware, nor spyware, nor malware, but it is being categorized as such. Currently adware, spyware, and malware are all negative terms, and the threat of such labels is enough to force action in one way or another. But, if you dilute it using it in edge cases, or cases that have *nothing* to do with the terms in question, you begin to erode the power of the term (see rape, domestic abuse, and racism for examples of such). And that would be a real shame to see happen.