Sam Ronson DUI Not Surprising To Her Friends

We're told ... in the past couple of months, Ronson has been hitting the nightclubs A LOT harder than she used to -- and for more than just work -- staying out longer hours ... and boozing more than ever.

Sources connected to Sam tell us ... even her ex-girlfriend Lindsay Lohan felt things were getting bad with Sam ... and she decided to minimize her contact with the DJ because she felt Sam wouldn't be a positive influence.