Some questions about Block eruptors

[blub]

Hi everyone,
I need some small electric heaters, and it looks like if Block erupters could come in an reasonable price range soon.

Has anyone expirenced problems with usb extension cords(2m)?
How much is maximum safe operation temperature?
And how much weight can I put on them?

[Slander]

what are you trying to heat? IF you are touching them you could heat say a coffee.

After about 6 inches they don't give of much heat unless you are trying to heat up your seed tray for your pot seed starter box. 

[blub]

well, a few different things,
yes coffe was one idea, but im quite unsure if the erupter can bear the weight of a coffepot+ doesnt run to hot with the coffepot on top.

then I have spot at the wall which gets wet every winter, unless i put a few watts of extra heating there.
heating some chemicals for quicker reactions
finaly warming some dough to let it rise quicker.