I'm not saying I think everyone should be building for IE8. I wish we could stop. But it's also not always just as easy as saying give up 5% of your potential users. The HN crowd is so often consumer focused and incredibly out of touch with the enterprise markets (this is not an argument against the parent comment, but an overall trend I notice on HN).
1) If it's actually 7% of your revenue as opposed to just global traffic stats.
2) If entrenched IE customers would actually stop using your product rather than just install another browser.
3) If the cost of maintaining shims, backwards compatibility and ultimately just falling behind the competition in both experience and features is less than that potential 7% market.
So my point is that of that 7% that are using older versions of IE, it's probably a much smaller number that would not be willing or able to use an alternate browser to run your web application if they find value in it.
To rephrase, makers of new tools, as a rule, tend to be forward-looking. This is what I'd expect. As corollary to this, at some point it no longer makes sense to support legacy technology. This produces a tradeoff within the aforementioned business case: is it worth the product constraints, effectively an externally imposed technical debt, to support that part of your market? How will you fare versus your competitors going forward if you do, or do not, support the legacy tail?
