-Yes, you have been unlawful present since your I-94 expired. You had better go to CBP to see whether you can change your I-94 to 09年12月30 if you think it was USCIS fault. Your H1 extension application may be denied or may be approved without I-94 (you need to get an H1 visa to activate it in this case) if you do not get the I-94 fixed. You had better use premium processing for the H1 extension to get the result quickly.
我在美国的合法身份应该是按照工作签证的有效期吧?
-No. This issue has bee discussed in this forum many times. See 置顶: 经验之谈:入境时,I-94被愚蠢的海关官员弄错了怎么办?