Process Explorer (or Monitor? there's no Process Manager) will show you some numbers regarding the memory usage - but unless you are the developer of that particular software and know exactly how it works internally, you have very little chance of interpreting them correctly. Long time ago, I tried to elaborate some more on
Wilders.
As for the e-mail scanner... well, I guess the guys have never heard of worms like Nimda, for example, or don't know how an e-mail scanner works. An e-mail is not a file originally - maybe after the mail client receives it and writes it on disk, but you cannot rule out the possibility of a bug in that e-mail program that actually executes an exploit during the processing of those data, before storing the file on disk.
The same is true for a Web scanner - yes, the web browser may (but certainly doesn't have to) write the downloaded files on disk (into the cache) - but if there's a bug in the browser or a helper module (and there have been a lot of them), the malicious payload may get executed before the file scanner has any chance to scan it - i.e. too late.
So there certainly is a reason for those additional shields - relying purely on a file scanner is naive.
Yes, WebRep is a community thing, based on users voting. Everyone is free do disable that feature.
