Everyone out here acting like failure to respond on #1 is negative. Maybe they got caught up in some shit, like life? Had that happen many times and they came back apologizing.
They may have been plotting on another date but it fell through. Nothing wrong with that, we all out here doing best we can. Was going to meet a girl Saturday at noon, texted her to say I'd been on a date Friday night and was, in fact, still in bed with said date.
"Shalafi you DOG! You go boy!"
NOTE: This woman lived with her boyfriend in a very open relationship. Just illustrating what can go on behind the scenes. Plus, it was pretty funny. We hooked up a year later. :)
Give them a day and a half, ask them out. Drop it if no response. See my other comments for more details on the asking bit.
#2: I fucking hate it, but it seems protocol to simply ignore anyone you're not interested in. Guess many people can't manage a polite thank-you/blow-off reply. And some people will take any reply to mean interest, no matter how clear your disinterest.