Just to be picky, it seems like the actual mining rate these days is closer to
4500/day. I get this using 7.5 blocks/hour from bitcoinwatch.com. Using 24
hours/day, and 25 bitcoins/block. This rate may well drop in the next 24 hours
when the difficulty rate jumps up by 25% which is also projected by bitcoinwatch.
Yes, that's one of the details.
When the computing power of the network rises or drops the difficulty adjustment will not be immediately, so there is a short timespan where too much blocks are found.
E.g. the difficulty doubles -> double the blocks where found per day before + we reach the next reward halving about a week ealrier.
So in fact the development of better mining tech or the rise of popularity has some effect.
It works in the other direction, too. If mining gets too unpopular or whatether reason the network power will drop, there will be less than 3600 Btc/day.
Remember that this effect is only active until the next difficulty adjustment.