Last I checked, about 400-500 had accepted. I put the blame squarely on me for not reading carefully, but also on LinkedIn for not warning me, but Google as well. Turns out Google has a group in your contacts for everyone you've ever emailed and it's at something like 6,000 for me, so I guess about 1/5th of those were on LinkedIn, who got invites.
Some of the invites went to people I'd banned from my sites for spamming, an old accountant I haven't talked to in ten years, and PR flacks I had arguments with over sending me press releases I didn't want. My LinkedIn account used to be a pretty well-curated list of people I'd actually interacted with in person before and done some business with, and now it's just a random hodge-podge of a bunch of internet strangers I crossed paths with at some point.
Supposedly LinkedIn has a karma system where you will be punished for anyone not accepting your requests.
You may end up banned from making future requests, although that might come as a relief and it sounds like LinkedIn might be BSing there given that combine that with support for mailing >1k people at once.
For whatever it's worth, I was one of the 1,138 – but, of course had no clue that I was x of N requests at the time rather than 1 of 1 or 2... but it seemed odd.
I've been on Metafilter for about a decade and I've interacted with Matt enough to know who he is – but also little enough to be completely surprised by the request.
I accepted it and then followed it up a shortly after with a note asking if we'd interacted more than I was aware of or if there was some other story to the request. It always seems better to be receptive but questioning to me – who knows what the story is behind all sorts of events in life..
Anyway, Matt was kind enough to respond and explain what happened. I thanked him and removed the connection at that point – I try only to keep connections with people I really interact with (or have interacted with) enough to want at least recall, but preferably sit down with and have coffee/beer/dinner, etc. if we were to cross paths.