I personally never respond to spammy email link trades, most of the time they don't even know who you are & you get buried on some 'link page'
If it wasn't a solicited trade & you don't know who it is, I wouldn't worry about it.
I prefer to link to those I know so I know they aren't going to pull my link 2 weeks later.
It's been said here before, be careful who you link to - think quality, not quantity
Ponygirl