Definitely Facebook. While I have an account, it's largely for when people tag me or invite me to stuff. I can easily sign on for long periods and not mind. And I communicate with most of those people over email anyway.
Second is Microsoft. While I use Skype at times, there are lots of other products in that space. I used to use webcalldirect instead of Skype.
I have voted for Microsoft. While Facebook would be second on my list, but it serves quite good to be in touch (once needed) with old time friends as they are not ones I'm getting in touch regularly through other communication channels. But that could be just my illusion - know few people who never had it and they don't regret it, and I don't think they lose something, so it is some sort of contradiction what I just said.
I have deleted my Facebook account a couple of times in the past when I realised that there was nobody on there that I wanted to keep in contact with who I didn't already see in person regularly or keep in contact via other means like email, phone, or text message. I do have an account now but I mostly use it as a news feed for my local police departments, the local animal rescue centre, and a couple of humorous pages such as one where the locals post dash cam video footage of other people doing silly things with their driving.
But it it all went away tomorrow, that'd be fine with me.
Didn't vote -- no none of the above option. I do use Amazon, but that is mostly due to health reasons; I don't get around as well as I once did and I have given up driving. Amazon is strictly a convenience for me, since I don't like asking the spousal unit or kids to run me places, and here is zero public transportation here.
As for the other four, I don't really have a need for any of them. I use google's search engine, more out of apathy than any other reason, the rest I don't use at all. Well, I do have one laptop left with windows, and the next time I am forced to reformat/reinstall it will probably become non-windows. In short, I could easily do without all five.
There are worse crimes than burning books. One of them is not reading them. Ray Bradbury
I am in complete agreement with those who voted Facebook in this forum. Nothing personal against it, and I acknowledge there are some interesting posts (I liked the funny ones), but mostly I always felt either depressed (because everyone seemed to be having a lot more fun, and a much more interesting life, than me) or just annoyed with some people posting to share almost every little thing they did (e.g. Working my garden - nothing against the gardeners out there, but really??).
Apple I have virtually nothing to do with despite a period in my career as a Mac programmer, owning a Newton and a PowerMac 601 that only ever ran the Newton developer kit and Bejeweled. These days if a client has a Mac, I pretend they're running Linux, which works for the most part.
Microsoft I deal with once a year because TurboTax. That's it. OK, I do like Flight Simulator, but I haven't "flown" lately.
Amazon. When people pay me to deal with AWS, or when I cannot purchase products through other channels like eBay or a direct vendor. I used to be a big Amazon fan, but for the last 5 years or so I've felt that they're too much a subsidiary of the US Government based on several different things they've done. I get my ebooks via the Nook store or directly from publishers. Without DRM, where possible.
So that leaves Alphabet/Google. I don't buy Google media products since I discovered that the "book" I "own" is in fact nothing but a 150-byte decryption key, so that any Google library I built could be wiped out any time they choose to invalidate the key or shut down the Google Play servers.
Cantankerous, ain't I?
When it comes to destroying a civilization, gas chambers cannot hold a candle to echo chambers.