Completing in the Small Blind

[DeeJ]

Apologies if this has been discussed elsewhere, so a link would be helpful if it has.

I was reading a comment - where I read it is probably crucial but I can't recall at the moment - and it said one of the most common leaks was failing to raise/fold in the small blind, but instead completing too often (in an unraised pot).

I often complete in the small blind as I get tremendous odds (especially at 15/30 when SB is 10), but the downside is you lose EV as BB has a free run whereas a raise will take BB out (some proportion of the time). Is this something people care about? Maybe it matters most if there's one or two limpers? Is this just a simple matter of preflop maths?