It hasn't exactly helped that many of them have actively become large and unwieldy organisations *on purpose* seeking to replicate corporate behemoths on the basis that weight of numbers in total equals strength. Many grass roots members haven't seen this move towards large hierarchical structures as being helpful on a day to day basis in the workplace.
I think this is a misrepresentation of what happened actually
- there are two processes at work in parallel that both lead to organisational inertia.
1. There is a professional bureaucracy that seeks to perpetuate and defend its position (and that can be subdivided into various broad camps - but all with that essential element in common), and some members will see building a complex corporate structure as part of that, although they are on the decrease in my view as people wake up to the power of combining network theory with organising as ways of reducing democracy.
2. The need for the union movement to create democratic structures for lay activists to organise themselves (by idenity, industry, sector, workplace, geographical area etc) which have come together piecemeal in different ways in different unions, some of which have then merged further complicating the issue and where no committee, branch, sector group or industrial joint committee or whatever is prepared to abolish itself or it's conferences, meetings, forums etc...
I make no value judgements on either and I don't think either are "bad" however they are clearly not adequate to face the challenges of the future - and they will change - though not necerssarily in the right way or in time.
On the size thing - there seems to be two equally valid schools of thought.
A. Small, proffessional unions that are generally 'apolitical' and focussed can create a clear and strong identity and win real influence in a single relatively skilled industry which is immune from offshoring/undercutting etc.
B. One (or two or three) big union(s).
