Hey guys,
I can tell from my own experience that I had my PayPal on -700 Eur, for 1 year, and nothing happened so far... ( I sold some ipods from china, but the quality was extremely bad ).
Also a friend of mine has his account on -1k ( or something like that ), for several years and still no problem.
I am just saying what happened in my case, but there is no guarantee it applies for everyone.
Regards