Decreasing[?] number of full nodes

[Nagan]

Let's say at the moment there are 200k of Bitcoin users on a network running 20-40k full nodes. All these numbers are somewhat out of the bushes, so please fix me if I'm wrong.
Apparently the number of full nodes is decreasing slowly but steady, and number will only shrink in the future, as new people are unlikely to use Bitcoin-qt. So what's left is: miners (less than 1000?), central wallet providers (hundreds?), serious exchanges(<100) and mentioned desktop clients. All this to assure healthy functioning of the network.

I have limited knowledge on the protocol design, but these numbers look somehow low. Even if the central core services will have a web of trusted high speed connections (this architecture was previsioned in the beginning), how stable is such system in the threat of botnet/Sybil attack where the number of cancerous nodes is approaching the number of the legitimate peers? Is there already a built-in mechanism to prevent that?

There's a lot of raving on how secure Bitcoin has become with increased hashing power, but aren't there any more dangerous problems the P2P level itself? It's like the botnets large enough are so easy manageable these days.

I bet this was discussed many of times, so could somebody please point me to the threads. Also any existing Bitcoin whitepapers out there related to the topic?

[niner]

Aren't the downloads of bitcoin-qt at an all time high?
I can't imagine why there would be fewer full nodes. 

[gyverlb]

Aren't the downloads of bitcoin-qt at an all time high?
I can't imagine why there would be fewer full nodes. 

It depends on how you define a full node (full might mean clients that allow incoming connections for example). As the OP didn't cite his/her sources there's no way to know what is being talked about.

[Nagan]

I don't remember if I've been high or just extremely stupid when I've posted the original topic, but it seems that I based it on remembrance of http://bitcoinstatus.rowit.co.uk/. Which is terribly outdated. The thing is that it's quite hard to find any graph with a daily node count.

By the full node I mean the one which receives/verifies/forwards transactions and blocks, and is connected for any useful amount of time. So the one that gives value to the p2p network.

blockchain.info has seen so far is 1,710,807 (http://blockchain.info/ip-log). There should be even more of them, so I missed number of users at least by the factor of 10x.

niner you are right, bitcoin-qt is definitely at the all time high. This is good enough already, but not all of these clients stay connected. I think most of the users just use application for transactions and then close it, as it consumes resources (Bitcoin-qt is not so aggressive to stay alive as say Skype).

I have found out some answers to my questions about security measures. There are some limits in the core protocol on forwarding messages etc.

Anyway, the name of the topic is probably quite misleading - I have nothing to base it at the moment. Still, it would be very interesting to collect the numbers in a graph.