There was a time, at least in my sphere, when going on a photowalk to see what you could encounter and visualise what photographs you may and then make them was seen as a solitary pursuit. In more recent times this seems to have evolved however into more of a group activity and indeed one where the emphasis is increasingly focused on the social aspect maybe?
These group walks can cover a wide range of photographic interests like scenics, architecture, nature, in-the-street and so forth. Notice I differentiate true street photography which, by its very interactive nature, remains a solo activity performed by the individual and much practiced documentary photographer.
A lot of these walks are organised by commercial photographers, camera makers, web pundits/forums and professional photo event leaders. I think they are popular as there is a feeling of safety in numbers and from the boost that comes from being with like minded people and participating in group activities.
But what of the photography? Well... from my own experiences, some people are only there for the social scene and the photography is secondary, many are gear heads and are there for the bragging rights and to sneer at your gear compared to theirs one way or another, only some are truly there for the photography. Most of those who attend are social and usually fun, a few can be quite anti-social, nasty and maybe deliberately disruptive. Some are very serious photogs indeed, are there on a mission, tend to hog all the best spots (often using tripods to block people out), can be rather intolerant of others, don't like people getting in their way and can be most vociferous about it.
The best walks are limited to just a few, say of no more than 8-ish, people with a shared interest. The worst are where people turn up mob handed with little in common, for instance one I attended was where thirty plus people arrived of widely varying degrees of expertise, capabilities, expectations and a varied sense of what constituted acceptable behaviour. The lack of organisation of the leaders did not help. Needless to say it pretty quickly turned into a chaotic scrum and after a few hours it degenerated further into what could best be described as a melee of disappointed and disgruntled folk all getting in each others way.
On the other hand, I have been on several small group walks over the years that have been really excellent, enjoyable and where I met some fab fellow photogs. I even made some nice photographs too. A great experience for everyone all round.
Remember though, one of the biggest challenges with all photowalks is that you have to work at the group's pace and in the common "group-think" direction. So If your intent is to do serious work uniquely of your own within a group you may find it frustrating and thus be better off going solo if you can. But don't be put off as group walks can often give you access to events, places and times that otherwise you might not be able to experience and you also can often meet some really great people too, just think small groups.
Now-a-days, when I want to do a photowalk on my own or maybe with one other, I talk about going walkabout with my camera instead, using the modern definition of walkabout being "temporary mobility". Also I am in the happy position that a walkabout with my camera can last several hours or several days or several weeks as opportunities present themselves or the mood takes me, so I feel the expression is quite appropriate. Most people get it.