it is rare.
one of the things that you have to ask yourself is this--were your cholesterol levels low when you were an omnivore or l/o vegetarian? if your cholesterol levels were in the low-end of normal, then perhaps your body doesn't produce enough. in which case, you likely need to get it from dietary sources (or consider medication--to me, neither choice is "vegan" and medication has side effects).
Before i was vegetarian, i had low cholesterol. my father who is an overweight omnivore also has low cholesterol (doctors marvel). his side of the family (brothers and sisters), all omnivores and mostly on fast food, have low cholesterol. When i went vegan, i was able to maintain it without trouble for 5 years. my levels were low, but not below my normal-low levels (which were just below the 'normal' range, but considering my familial history, it wasn't a concern).
last year, we discovered that they'd become too low. with connections to brain function, cognative ability, and depression and anxiety, it wasn't something that i wanted to mess with. I started to exercise more (as this is often a method of increasing "good" cholesterol) and consume coconut oil (which supposedly helps stimulate the process). After six months of experimenting, we (doctors and I) decided to consider eggs and/or medication.
Since i didn't feel comfortable taking medicatin, they set my minimum weekly intake of eggs at 6. after 3 months, my levels were up, but still low. we moved my egg intake up to 12. my cholesterol went up again, but again was below my normal range. i was feeling better though. Finally, when they suggested that i eat 18 or more eggs a week, i decided that i would also add in full-fat, raw, nonpasturized dairy products (cheese; homemade ice cream made with fresh cream, milk, etc; and butter).
currently, my egg intake is down to about 6 a week *if* i remember to get two servings of dairy per day. This is not an easy task for me, overall, simply because it was so easy being vegan.
feel free to PM me.
PS: saturated fats aren't a problem, if they are natural such as the saturated fat present in olive oil. in fact, we need some saturated fat. the transfats, hydrogenated oils, and other perversions of fat (such as heating vegetable oils) is what causes problems.