Do you need another reason to avoid "sp_" prefix?!
Note: Do not preface your stored procedure names with sp_, because doing so reduces performance. When you call a stored procedure that starts with sp_, SQL Server always checks the master database first, even if the stored procedure is qualified with the database name.
from
Designing Data Tier Components and Passing Data Through Tiers, section titled "Recommendations for Using Stored Procedures with Data Access Logic Components".
