What the hell - everyone else is talking about it . . .Psychology and statistics best determine whether two people will have a happy marriage. At least that’s the claim made by an online dating service that’s patented its matchmaking formula. EHarmony.com Inc. this month received U.S. Patent No. 6,735,568, which describes a ‘‘method and system for identifying people who are likely to have a successful relationship.’’ Not surprisingly, critics and competitors trash eHarmony’s process as overly scientific — some dismissing the so-called ‘‘love patent’’ as gimmicky.