How does a block have essentially no transactions besides the block reward?

[Severian]

My question is probably a function of my ignorance of the deeper parts of the protocol, but does this happen often?

http://blockchain.info/block-index/297083/00000000000001af07240240994e4dabf9856cfc25c7bc6bd72bbb0c9193d19f

Block #199464
Summary
Number of transactions   1
Output Total   50 BTC
Estimated Transaction Volume   0 BTC
Transaction Fees   0 BTC
Height   199464 (Main chain)
Timestamp   2012-09-19 01:18:11
Received Time   2012-09-19 01:18:35
Relayed By   Deepbit
Difficulty   2,694,047.95295501
Bits   436615736
Size (kB)   0.2177734375
Version   1
Nonce   3420561926
Block Reward   50 BTC

[maaku]

I'll give you a hint: look at the timestamps/received-time of that block and the one before it.

[jgarzik]

Miners choose which transactions to include in a block.

A valid choice is "no transactions" [besides the required coinbase transaction].

[Severian]

Blocks 199462-199465 were all created within a minute of each other, sequentially. Is that a function of how busy the network is or is it a decrease in difficulty?

Miners choose which transactions to include in a block.

A valid choice is "no transactions" [besides the required coinbase transaction].

I now grok the no transactions flag. Thanks.

[jgarzik]

Blocks 199462-199465 were all created within a minute of each other, sequentially. Is that a function of how busy the network is or is it a decrease in difficulty?

Random chance.  Sometimes miners find a new block within seconds of the previous block.  Sometimes miners find the next block an hour or two after the previous one.

10 minutes is only the average target.

Miners choose which transactions to include in a block.

A valid choice is "no transactions" [besides the required coinbase transaction].

I now grok the no transactions flag. Thanks.

Not sure what you mean by "flag" but ok

[Severian]

Random chance.

This makes me like this protocol even more.

Not sure what you mean by "flag" but ok

Flag, option, choice, checkbox, click-the-thingy...

Give a noob a break.