fung:
I don't see how they could.
For example, just because you know my e-mail is matt@investorshub.com doesn't mean a thing.
My servers are in Missouri, I don't use iHub connection over the Internet, and I'm in Tallahassee. So that tells you nothing about where my lard butt is sitting here typing this message.
But let's say you are using hairy_midget@fungslocalisp.com ... even then, just because they "know" your ISP doesn't mean they can crack your computer.
A bigger problem with knowing your e-mail is for a hacker to receive an e-mail from you. Every e-mail you send out has your IP address attached to it (the virtual house number for your pooter), so they could use *that* to hack your computer. But really, the majority of hacks are just random....based on scans they do of networks.
Have you ticked somebody off?