I don't understand what you're saying here. All of my mail is backed up by me, with a redundant copy on the mail server. I'll agree trusting third parties is a bad idea on a few levels, but if you aren't running your own mail server, POP and IMAP are equivalent for mail safety.
Well, if you can correct me on this point that's great, but as far as I'm aware, most mail clients don't have a system in place to spot a situation where say a load of mail has disappeared from the IMAP account server-side. When I've asked various people questions before on this topic they don't really know what to expect in that situation, except for the logical-but-horrifying "start synchronising the deletion of mail client-side until both match up" scenario.
Based on my assumption, IMAP doesn't seem like a very safe option unless the client is also in control of the server, or there are extremely decent communication and strategies in place for such a scenario, let's say Google has a serious mail data loss incident, so they immediately switch off IMAP services to ensure that clients don't lose their copy of the data as a temporary measure until the issue is resolved one way or another.
For those paranoia-nerds out there concerned about a company losing your email, I reply with "I think I'll trust a multi-million dollar company's backup systems and redundant servers to keep my mail safe rather than a $100 USB backup drive".
Let's say I have a Google Mail account and I use IMAP. I don't pay Google anything for this service. How do you propose in this situation that Google has my best interests at heart if something bad happens?
Virtually every free mail provider out there has had a data loss incident at one time or another. AFAIK, if the data loss turns out to be irreversible, the company's response is:
<shrugs> Sorry...
If however I am responsible for my own data's safety, then I can take as many measures as I deem appropriate, and if something bad happens that makes a mockery of those measures, I can choose to invest in say data recovery services or not, for example. If a company hosts my data for free, I don't have that choice. I simply have to assume that their employees are a) competent and b) honest as well as their equipment and backup strategies are all in decent working order. One problem with complicated backup strategies is, how often do they get thoroughly tested. Usually backup strategies are tested in very small-scale scenarios.
Yeah, mail at the access speed that the service currently allows based in part on the strength of your connection to it is so superior than what you can do with it under outlook stored on your own computer.
Give me an example of what you mean here. I've yet to see something that made me think "I really wish I had a mainstream webmail system rather than Thunderbird".