Not the best of rivers but flush missed, still FOLD?

[nextgenneo]

Vil is 27/10/1 w/ fairly high flop and turn aggro #s but only 1 on the river and 1 preflop (so could easily flat big hands pre)

Hero dealt 5[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/club.gif[/img]

Button HERO ($395.60)
SB Alfs ($657.80)
BB <font color="#C00000">IFishNTell ($474.80)</font>
UTG maveryc77 ($429.22)
UTG+1 spund14 ($240.90)

Preflop: , 1 fold, spund14 calls 4.00, HERO raises to 18.00, 1 fold, IFishNTell calls 14.00, 1 fold.

Flop (42.00) 5 [img]/images/graemlins/club.gif[/img] T [img]/images/graemlins/diamond.gif[/img] 3 [img]/images/graemlins/club.gif[/img]
IFishNTell checks, HERO checks.

Turn (42.00) 6 [img]/images/graemlins/diamond.gif[/img]
IFishNTell bets 30.00, HERO raises to 120.00, IFishNTell calls 90.00.

River (282.00) 7 [img]/images/graemlins/spade.gif[/img]
IFishNTell moves all-in for 336.80, WTF?

<font color="blue">Big bet vs a passive player = fold?</font>