According to my little knowldge these are the challenges of BA

1. He always keep one thing in the mind that Technology is important but Business is Manditory

2. He always prfer to listen the client requirements and make sure that there should not be any gaps in gathering of the requirement.

3. Preparing Vision and scope document plays a vital role he always gives his boundaries to the customer what he can do and wht he can't

4. He has to make sure that testing as to done parallely so that he can rectfy the things in intial stages.

5. He has to give Business Requirement specifiaction in a clear and detailed manner.

6. He should ready to accpets the mistakes and should be open to correct his/her mistakes

I am not saying these are the real challeges please let me know if you feel that is there any thing to Include or exclude

Some of the challenges a BA faces during the lifecycle:
1. a PM who does not trust their resources to complete the job or the tasks they are paid to do...instead making them a 'glorified secretary'.
2. a PM who does not clear the path of obstacles for the Business Analyst when the analyst is collecting requirements. For example push back business users not making time available not supporting process improvement opportunities
3. a PM who commits to timeframes without consulting the person responsible for the deliverable first.
4. Team members who care more about formatting then content causing deliverables to be delayed or very slow moving.
5. Lack of clearly defined roles and responsibilities between team members.
6. Lack of clearly defined project expectations between groups.
7. Changing requirements of course...but that is unavoidable the issue is how the PM manages changing requirements that makes it challenging or not. For example are they putting it into a future release are they buying more time etc.
8. People with limited knowledge wanting documentation for the sake of documentation when they don't really know the value of the document being requested to be developed or requesting documentation at an inappropriate time within the SDLC causing constant rework.
9. a PM that does not have your back when the noise starts to get loud. A PM and a BA should tag team each other and support each other no matter what the case. Every project will have difficult times but the PM and the BA need to remain a united front at all costs in order to maintain social integrity the duration of the project.
10. Gaps in requirements (all BA's have them...it is the size of the Gap that differentiates a good BA and a novice).

These are just a few. There are always challenges regardless of the role you play. These are off the top of my head that could potentially be the biggest pain points.