deepbit can already detect botnets
Well first off, a pool has no vested interest in botnets. More hashing power to them means more money to them. Tycho has more or less been a standup guy in the bitcoin community, which is cool, but if botnets become more profitable I wouldn't be surprised or vexxed if he suddenly "stopped finding" botnets.
Secondly a botnet isn't exactly hard to detect. When one account suddenly has 5000-500000 IP addresses popping data in for it, you'd have to be blind to not 'detect' it.
I don't know how can anyone come to such conclusions. Hacking or seeding malware and taking control of other people's computers without their consent is straight up illegal and criminal in most countries if not all. You think pool owner knowingly would want to be associated with such activity and profit off of it? [insert facepalm]
Don't be juvenile. Bitcoin itself is a nebulous gray area of legality. By your logic pool operators would not want to be associated with bitcoin at all. A reasonably large pool has a pretty easy claim to deniability in terms of botnet association. They have thousands of clients pummelling their servers with getwork reqs and submitted shares, if they would like to keep a lax watch on their ip tables and gain a very tidy sum of money, why do you think they wouldn't?
Let us imagine some nightmare scenario like the OP suggests. A million zombie computers come online operated by a few botnet owners, they average 100MHash/sec each, running about 100 THash/sec total. The network has grown by roughly 10x in size, normal miners are essentially squeezed out of the network. You are saying that all the pool operators who have been RAKING IN money off bitcoin are suddenly going to say "oh dear, botnets are illegal, I guess we'll all have to shutdown our magical money fountains?"
That's in a worst and most obvious case scenario as well. Say only 4THash came online of botnets, comprising 1/4 the total hashrate of the network, and therefore whatever pool operator welcomed botnets now has easily gobbled up 1/4 of the hashrate, no pool would happily accept that? Not to mention the pools that DONT accept botnets see their own slice of the pie shrink considerably, diminishing their returns by a lot. Enjoy living in fantasy land.
Secondly a botnet isn't exactly hard to detect. When one account suddenly has 5000-500000 IP addresses popping data in for it, you'd have to be blind to not 'detect' it.
If you were a smart botnet operator, could you not have all of your controlled machines mining for a bitcoind running on one of the machines?
You could of course, but it's a hassle to run a large pool, have it able to have the capacity to handle such a flood of requests, and also sets up a single nodepoint to be shutdown if authorities want to crackdown on you. A pool is easier, just point at it and everything is set up for you. Also makes a nice source for laundering bitcoin.