> First of all, these are integrations that you explicitly install (like installing an app), so that's obviously opt-in.

I don't think the privacy/security concerns should be so cavalierly dismissed. I'm sure I'm not the first to open a friend or relative's computer and discover half a dozen browser toolbars installed. The same is likely to occur here. HN readership may be pretty cautious about this stuff, but HN readership isn't Gmail's only user base.