Zivush - 5:06 pm on Oct 24, 2011 (gmt 0)
My second best traffic website has almost 1000 of these broken links reported in WMT.
No worries. Ignore these spammers - These are links mostly from Chinese websites that start to flourish after Panda attacking innocent sites.
My logic is on the same page with --
In my opinion, rankings may be affected only if your internal links points to 404 pages.
If external links point to 404 pages should not be a problem at all, you cannot control this.
I don't think 301 is a good idea as you adopt these URLs (someone mentioned this).