Should we be worried or are the US paranoid?

Complex issues I know as we already incorporate their technology and hard to stop it now, but would China really want to dump on their own doorstep?  Who would trade with them if they were found to be carrying out activities that were a high security risk?

Is it OK if they are kept out of the 'core'? Can cyber security organisations be vigilant enough?

Any thoughts? Are you worried? Do you care?